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Behavioral Traffic Safety Messaging on Variable Message Signs (2022)

Chapter: Part 2 - Conduct of Research

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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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Suggested Citation:"Part 2 - Conduct of Research." National Academies of Sciences, Engineering, and Medicine. 2022. Behavioral Traffic Safety Messaging on Variable Message Signs. Washington, DC: The National Academies Press. doi: 10.17226/26656.
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P A R T 2 Conduct of Research

2-3   Problem Statement Variable message signs (VMS) (also sometimes referred to as changeable, electronic, or dynamic message signs) are used to provide future and real-time traffic-related information to drivers while en route to their destination (Dudek and Huchingson 1986). Many agencies also use these signs to display behavioral traffic safety (BTS) messages when the signs are not being used to display other traffic-related information. These types of messages encourage safe driving behaviors (i.e., wearing seat belts, not drinking and driving, etc.). The FHWA first officially stated that displaying BTS messages on VMS was appropriate in a 2001 policy memorandum (Johnson 2001). That memorandum was superseded by an additional policy memorandum regarding safety message signing and then in language within the 2009 edition of the Manual on Uniform Traffic Control Devices (MUTCD) (Peters 2002; MUTCD 2009). In 2021, FHWA issued additional guidance in an official ruling regarding nonstandard syntax used on such signs (Kehrli 2021). Currently, the ways in which agencies develop and display BTS messages on VMS vary widely across the country. More importantly, little guidance is currently available as to how BTS messages should be designed and presented on VMS. Current message design guidance for VMS was developed for traffic management information applications (Dudek and Huchingson 1986; Dudek 2004; Dudek 2006). In such situations, the emphasis is on ensuring the message is easily under- stood, provides information critical for making a better driving decision, and does not overload the driver with excessive information. Retention of all the information provided in such messages is usually essential for the motorist to make appropriate decisions and take proper actions. For BTS messages, however, information processing and retention demands may be much less sig- nificant, and the information itself may not warrant immediate decision-making and reaction by most drivers. This does not mean that VMS operators need not be concerned with the length or content of BTS messages or how they are formatted and displayed. Poorly designed or confusing BTS messages could attract too much visual and cognitive attention by the driver and potentially reduce safety. It is, therefore, necessary to determine what constitutes effective practices regard- ing the design and display of BTS messages and to develop implementation guidance on BTS message design and display that is useful to VMS operating agencies. C H A P T E R   5 Background

2-4 Behavioral Traffic Safety Messaging on Variable Message Signs Previous Research BTS Messaging Concepts and Effectiveness BTS messaging on VMS is a specific strategy within the overall context of roadway safety com- munication efforts and campaigns. Such campaigns typically have one or more of the following goals (Delhomme et al. 2009): • Provide information about new or modified laws. • Improve knowledge and awareness of new in-vehicle systems, risks, etc., and the appropriate preventive behaviors. • Change underlying factors known to influence road-user behavior. • Modify problem behaviors or maintain safety-conscious behaviors. • Decrease the frequency and severity of traffic crashes. Multiple theories have been put forth to explain driver risk-taking behavior as well as how such behaviors can be altered (Hoekstra and Wegman 2011; Robertson and Pashley 2015; Fishbein and Ajzen 1975; Triandis 1977; Rosenstock 1974; Rogers 1975; Petty and Cacioppo 1986; Wilson, Lindsay, and Schooler 2000; Prochaska and DiClemente 1983; Carver and Scheier 1981; O’Keefe and Jensen 2008; Millar and Millar 2000; Elliot 1993; Lewis, Watson, and White 2008; Lewis, Watson, and Tay 2007; Guttman 2015). In turn, these various theories and models have led to different message strategies and styles to elicit the desired attitudinal or behavioral changes of interest. The following key points can be drawn from that literature: • BTS messages need to be credible, trustworthy, consistent, clear, persuasive, relevant, and appealing to be effective. • BTS messages can present a “gain” to be had by avoiding some behavior or by adopting a safer behavior (i.e., a gain-framed message) or a “loss” to be experienced by engaging in the undesirable behavior or failing to adopt the safer behavior (i.e., a loss-framed message). Gain- framed messages tend to be more effective than loss-framed messages, although there are examples where loss-framed messages have had the desired effect on drivers. • BTS messages can be designed to be objective and factual or can be designed to elicit an emo- tional appeal (either positive or negative). Emotional appeals tend to be more effective than objective, factual messages. In addition, negative appeal messaging may have a greater influ- ence immediately after seeing the message, but positive appeal messaging may be more effec- tive over time. • Males tend to be less influenced by negative, fear-appeal messages than females. Instead, the use of humor in BTS messages appears to be more effective in influencing males than females. • Excessively humorous BTS messages may entertain those viewing the message without get- ting them to accept or understand the safety analogy being presented. • Using numbers and statistics to show the magnitude of the road safety problem does not appear to consistently affect driver attitudes or behaviors due to optimism biases (i.e., drivers overestimate their competency and the degree of control they have over events such as crashes). • Messages that attempt to shame or label certain target drivers may not be effective, as those target drivers may not identify with those being mocked or insulted in the message. • Messages pertaining to enforcement efforts and consequences can raise awareness of the threat of apprehension and penalty but may also elicit the motivation to avoid being caught rather than appealing to the desire to behave properly. • Humor (parodies, witticisms) and pop culture references need to be familiar and liked by the target drivers to be effective. In fact, negative appeal messages utilizing these features may be considered in bad taste or even offensive.

Background 2-5   Display of BTS Messages on VMS The traveling public has tended to view the display of BTS messages on VMS as useful and valuable (Benson 1996). In past studies, 79 to 95 percent of travelers surveyed remembered encountering a BTS message on VMS (Schroeder et al. 2016; Tay and Debarros 2008; Rodier et al. 2010). Most drivers support the display of BTS messages on VMS as a good reminder about proper driving behaviors (Rodier et al. 2010; Schramm et al. 2012; Boyle et al. 2014; Mitran, Cummins, and Smithers 2018). Even so, drivers value real-time information about traffic con- ditions, roadwork, and incidents over the presentation of BTS messages on VMS (Rodier et al. 2010; Harder and Bloomfield 2008; Mounce et al. 2007). Not all BTS messages are perceived as equally important or useful to drivers. Rather, the per- ceived value or importance of a BTS message varies based on the content of the message and the gender and age of the driver. As might be expected, the effect of VMS-displayed BTS messages on immediate driver behavior has been mixed. For example, studies have found little or no change in seat belt use or speeding in response to BTS messages targeting those behaviors (Rodier et al. 2010; Tay and Debarros 2010; Jamson and Merat 2007; Schroeder and Demetsky 2010; Cooper and Mitchell 2002). Likewise, the effects of displaying BTS messages about state move over laws or warnings about possible animal crossings have a very limited effect on speeds (Hardy, Lee, and Al-Kaisy 2006; Megat-Johari et al. 2021). However, other studies suggest that messages discour- aging cell phone use or tailgating may yield some changes in those types of behaviors (Tay and Debarros 2008; Kostyniuk et al. 2014; Cheng and Firmin 2004). It is important to acknowledge that behavioral metrics such as speed changes do not always reflect the fact that a message has heightened driver awareness about those risks even though their behavior has not changed (Jamson and Merat 2007). Finally, just as it does for real-time traffic management messages, the effectiveness of BTS messages on VMS also depends on drivers being able to understand the message. Poorly designed messages that are not easily and quickly understood can create confusion and increase information processing times, which can cause motorists to slow down to allow more time to view and read the messages (Harder and Bloomfield 2008; Jeihani et al. 2018; Guattari, De Blasiis, and Calvi 2012). VMS Message Design Guidance For traffic management messages, the amount of information (or “load”) presented is quantified in terms of information “units,” which are simple answers to the following types of questions: • What is the problem? • Where is it located? • When will it occur (for advance notification messages)? • Which lanes are closed? • What is the effect on travel? • Who is the message intended for? • What action do I need to take? Drivers are not usually able to stare continuously at the VMS message as they approach it. Rather, drivers alternate between glances at the sign and glances at the roadway. If more infor- mation is presented than can be effectively perceived and processed by drivers during the limited viewing time available as they approach the VMS, one of two possible outcomes typically occurs: • The driver will not be able to correctly perceive and process all the information provided, leading to confusion and incorrect driving decisions or

2-6 Behavioral Traffic Safety Messaging on Variable Message Signs • The driver will slow down to create more viewing and reading time of the message before passing the sign, creating turbulence in the traffic stream and speed differentials with other vehicles on the roadway. Past research has shown that various VMS design and message formatting and display char- acteristics can adversely affect driver information perception, processing, and retention abilities. For example, research has shown that messages should not utilize scrolling lines, animation, dissolving or exploding characters, or flash certain portions of a message; doing so increases attentional demand and degrades comprehension and retention of the information presented (Dudek et al. 1978; Dudek et al. 1981; Dudek and Ullman 2002). Research has also shown that care should be exercised when trying to abbreviate a word or phrase in a message, as not all abbreviations will be well understood by drivers (Hustad and Dudek 1999; Durkop and Dudek 2000). Poor understanding will increase processing times for the message and may even lead to incorrect interpretations of the message. The way a message is formatted on VMS also affects how quickly and accurately drivers can process and retain the message (Dudek et al. 1978). Ending a unit of information on a line and starting a second unit of information on that same line may make it possible to fit more words onto VMS, but the overall message may not be easily understood, as shown below. MAJOR ACCIDENT AHEAD USE LEFT LANE MERGE RIGHT In addition, each phase of a two-phase message should be understandable by itself, regard- less of the order in which the phases are viewed by an approaching driver. Messages that rely on reading the first phase before reading the second phase can seem confusing if read in the opposite order, as shown below. RIGHT LANE CLOSED AHEAD FAIR TRAFFIC EXIT HILLSIDE TURN RIGHT Furthermore, although drivers can typically process and retain up to four units of informa- tion in a traffic management message, it is more difficult for motorists to process and retain that information if it is presented all at one time (Dudek et al. 1978). Consequently, it is recom- mended that no more than three units of information be displayed in a single VMS phase. If four units are to be displayed, they should be split across two VMS phases. The information units should be organized to keep compatible units of information together on the same phase so that each phase of the message is understandable by itself (Dudek et al. 1978). This way, it will be easier for drivers to quickly understand each phase of the message regardless of which one they see first as they approach the sign. For a traffic management message, information units relating to the problem and its location are compatible, the action to take and the audience that should take that action are compatible units, and two actions to take together would be compatible units, etc. If compatible units are kept together, a message phase will be understandable by itself. Conversely, if compatible units of information are not kept together, each message phase will likely not be understandable by itself (Dudek 2006). Although BTS messages are not typically designed and formatted the same way as traffic management messages, these basic principles are still valid. On January 4, 2021, FHWA issued an official ruling, Uses of and Nonstandard Syntax on Changeable Message Signs (Kehrli 2021). The ruling responded to several questions regarding

Background 2-7   the use of unconventional wording in VMS messages and public input into the development of VMS messages. Although not focused exclusively on BTS messages, much of the ruling pertains directly to such messages. As part of the ruling, FHWA encourages the display of BTS messages on VMS to be done judiciously as part of “larger safety campaigns that rely on other media as their principal means of communicating the campaign message.” In addition, the display of such messages should be coordinated with enforcement efforts regarding the problem behavior. FHWA suggests coor- dinating BTS messaging with the National Highway Traffic Safety Administration’s (NHTSA) annual communications calendar (NHTSA n.d.) whenever possible to encourage consistency in national behavioral safety outreach efforts. FHWA also encourages agencies to consider the type of roadway where VMS are located when selecting BTS messages to display. For example, a message about watching for children as they return to school may be appropriate for VMS on an arterial street near a school but not for one located on a high-volume urban freeway where there is little chance of encountering children on foot. Some agencies have utilized contests or other means of soliciting ideas from the public for BTS messages to display on VMS. FHWA recommends that public input be primarily used to identify messaging ideas, with the responsibility for designing and formatting messages left to agency staff with knowledge of proper VMS message design principles. The January 2021 FHWA ruling discourages the use of wit, overly informal words and phrases (colloquialisms), and pop culture references as part of BTS messages on VMS over concerns that such messages may not convey clear and consistent meanings to drivers. The use of such expres- sions may also degrade motorists’ respect for VMS as a traffic control device and can increase the amount of time it takes motorists to recognize and process VMS messages overall. Finally, FHWA notes the following types of information are inappropriate to display on VMS, even as part of a BTS message: • Website (URL) addresses, domain names, hashtags, or electronic device application names. • Telephone numbers. • Statistics (highway fatalities, citations issued). • Personal safety messages not related to traffic. • Public awareness campaigns not related to traffic. • Public safety alerts (except Homeland Security and AMBER alerts). • Public service announcements. • Sponsor acknowledgments. • Weather conditions or advisories except as related to expected adverse road-weather conditions. • Full-motion video, flashing symbols, or other graphic features or icons not specifically pro- vided for in the MUTCD. Project Objectives The objective of this research was to develop a guide for the use of VMS to deliver BTS mes- sages to motorists. The guide would address all aspects of VMS use to display BTS messages from policy development through implementation and consider the following topics: • Current state of the practice, both nationally and internationally. • Administrative policies and procedures that define how safety messages are selected and displayed. • Types or categories (e.g., theme, style) of BTS messages to use. • Message selection procedures (who, when, where, how, and why).

2-8 Behavioral Traffic Safety Messaging on Variable Message Signs • Message characteristics that promote motorist understanding of VMS (e.g., message design, size, color, speed of switching between message phases). • Strategies that can enhance the understanding of various driver groups (e.g., older drivers and bilingual drivers). • Differences in use between rural and urban environments. • Effect (both intended and unintended) and effectiveness of traffic safety messages. • Barriers to implementation. • Recommendations to enhance coordinated traffic safety strategies.

2-9   BTS Message Creation and Approval As part of this research, the research team surveyed state and local agencies to determine existing policies and practices regarding BTS message creation, approval, and display on VMS in their jurisdictions. Researchers also requested BTS messages that the agencies had posted over the past year. Appendix B provides a summary of the survey questions. Surveys were sent to all 50 states and 20 municipalities and toll agencies. The research team received responses from 38 of the agencies. Even though many agencies did not respond to all questions, several insights were gleaned from the input received. Nationally, two basic approaches exist for the creation of BTS messages for VMS display: • Agency staff with operational responsibilities for VMS messaging rely on requests from the state office of highway or traffic safety responsible for handling the NHTSA safety grants program to post a proposed BTS message. • VMS operating agency generates ideas for BTS messages and goes through an internal review and approval process before posting. Over 70 percent of agencies responding to the survey have expanded their BTS messaging efforts on VMS beyond the scheduled national and statewide safety campaigns throughout the year. Specifically, holidays, special events such as football games or concerts, and weekends are often targeted with BTS messages on VMS. A few agencies have initiated weekly BTS messages (i.e., Message Mondays, Think Thursdays). Although the overuse of such messages is believed by some agencies to potentially reduce driver attention and sensitivity to other VMS messages, those that displayed more frequent BTS messages felt that doing so provided continuous motorist reminders to drive safely. Increasing the display of BTS messages also increases VMS use overall, particu- larly in locations where the signs are not frequently activated for traffic management messages (i.e., rural corridors, lower volume roadways). Agencies that develop their own BTS messages for posting on VMS typically create teams or committees to develop, review, and approve BTS messages that will be displayed. These teams or committees meet as often as needed to support the frequency of posting new BTS messages. The makeup of these teams or committees varies in size and organizational representation within the agency. Message creation teams or committees generate most of the message ideas that get reviewed and approved; however, most agencies that responded to the survey noted that they also occasionally receive ideas from other agency staff and the public. Oftentimes, these sugges- tions occur because someone saw a BTS message on VMS in another jurisdiction and thought it would be a good message to display. A few agencies have also sponsored contests through their websites or with the media to gen- erate BTS message ideas. Such contests require allocating staff time to review and prioritize the C H A P T E R   6 Current Practices Regarding BTS Message Design and Display on VMS

2-10 Behavioral Traffic Safety Messaging on Variable Message Signs suggestions. Furthermore, a decision needs to be made beforehand as to how many suggestions are going to be used and the schedule of their use. One agency indicated they received pushback from their districts about the number of BTS messages that headquarters requested be displayed after sponsoring one such contest. BTS Message Design Policies Most agencies responding to the survey indicated they follow the MUTCD and their agency’s VMS message policies and procedures when designing the BTS messages for their signs. Keep- ing the message as short and simple as possible, on no more than two phases, was a common policy, as was ensuring the message pertained specifically to driver and traffic safety topics. A few agencies limit BTS messages to a single phase on VMS, and some require that BTS messages include actionable information when displayed on limited-access highways. BTS messages used by most agencies are strictly text-based. However, at least two agencies allow a limited number of text and graphic BTS messages to be used on those VMS that can support those types of displays (see Figure 11a and b). BTS Message Display Criteria Many agencies did have more specific information on when they would allow BTS messages to be displayed on VMS and for how long. A summary of the criteria is shown in Table 1. It is common practice to restrict the display of BTS messages during peak travel periods, particularly (a) (b) Figure 11. BTS messages that include graphics displayed on VMS from (a) the Florida Department of Transportation (FDOT n.d.) and (b) the North Dakota Department of Transportation (NDDOT 2015).

Current Practices Regarding BTS Message Design and Display on VMS 2-11   Agency Display Criteria Colorado DOT • Messages used sparingly during peak periods. • Messages rotated for campaigns lasting more than 1 week. • Message displays not to exceed 3 hours per day per sign. Connecticut DOT • Message displays limited to no more than 2 weeks at a time per campaign. Florida DOT • Messages not displayed during peak travel periods. • Message displays limited to no longer than 2 weeks total duration per campaign. • Message displays not to exceed 2 hours per day per sign. Iowa DOT • Messages displayed every Monday (Message Mondays). • Other messages are displayed for holidays or other special events as well . Idaho DOT • Messages generally displayed 1 day per campaign. • Messages typically displayed 4 to 5 times per year. Missouri DOT • Messages generally displayed for 1 week per campaign. North Dakota DOT • Message displays are not to exceed 3 days at a time. New Jersey DOT • Messages not displayed during peak travel periods in urban areas. • Message displays limited to no longer than 1 week total duration per campaign. • Message displays limited to no more than one campaign per month. • Message displays not to exceed 2 hours per day per sign. New Mexico DOT • Messages not displayed during peak commuter periods in urban areas. • Message displays limited to no longer than 1 week total duration per campaign. • Message displays limited to no more than one campaign per month. • Message displays limited to no more than three campaigns per year. • Message displays not to exceed 2 hours per day per sign. New York Thruway Authority • Message display duration depends on the length of the campaign but typically should not exceed 4 days. Pennsylvania DOT • Message display times can vary, but typically are 6 hours at a time per sign. South Carolina DOT • Messages are typically displayed for 3 days at a time. • Messages for most campaigns are displayed during the week (Monday–Friday). Driving under the influence (DUI) messages are displayed on weekends. South Dakota DOT • Message displays for traffic safety campaigns should not exceed 7 days per month per sign. • Message displayed every Thursday (Thinking Thursdays) from midnight to midnight on available VMS. Tennessee DOT • Messages not displayed during peak periods in urban areas. • Message display time not to exceed 6 hours per day per sign (typically 9 a.m. to 3 p.m.). Texas DOT • Message displayed every Monday (Message Mondays) that runs from midnight to midnight unless a higher-priority message needs to be displayed. • Messages are also created for events (holidays, football games, etc.). Display duration for those messages varies depending on the event. Virginia DOT • Messages should not be displayed for campaigns that are more than 2 weeks out. • Messages not displayed during peak travel periods. • Message display time not to exceed 4 hours per day per sign. NOTE: DOT = Department of Transportation Table 1. Examples of agency BTS message display criteria on VMS.

2-12 Behavioral Traffic Safety Messaging on Variable Message Signs in urban areas. However, considerable variation is evident among agencies as to the number of BTS messages allowed to be displayed on VMS and the duration of those displays. A few agencies provide weekly BTS messages on VMS to motorists in their states, whereas others limit the number of BTS messages that are displayed on their VMS to approximately four to five times per year in conjunction with national or state overall safety campaigns. Agencies also differ in how long they allow a BTS message to be displayed on each VMS. In some jurisdic- tions, each BTS message is displayed continuously but only for a single day or over a weekend— unless other traffic management messages need to be posted on the sign. Other jurisdictions display BTS messages periodically over a 1- or 2-week period, with the duration of display limited to between 2 and 6 hours each day during that period. The decision on which VMS are used for displaying BTS messages depends on the number of signs an agency operates and whether any of those signs are being used to automatically display real-time travel time messages. Agencies with only a few signs tend to post the BTS messages on all their VMS unless there are higher-priority messages to be displayed. Conversely, agencies with larger numbers of VMS distribute BTS messages strategically throughout their jurisdiction to better manage how many times a driver might see the messages during a single trip. Another technique used to avoid overexposing a BTS message is to create multiple messages associated with a specific traffic safety theme and disperse the different BTS messages among the available VMS so that drivers do not see multiple instances of the exact same message. Regardless of the display criteria followed, all agencies reported that BTS messages were the lowest priority of possible message types to be displayed on VMS. Characteristics of BTS Messages Displayed on VMS Agencies use VMS to disseminate BTS messages on a wide range of safety topics. Table 2 presents the distribution of common BTS message safety topics, based on a review of over 1,000 actual messages provided by 29 of the agencies responding to the survey. Messages about seat belt use, drinking and driving, and distracted driving were the most common safety topics found in BTS messages on VMS, collectively accounting for more than 50 percent of all messages reviewed. Topic Percent of All BTS Messages Encouraging seat belt use 20 Discouraging drinking and driving 18 Discouraging distracted driving 15 Discouraging speeding 8 Encouraging safe driving in general 7 Encouraging safe driving in work zones 6 Encouraging safe driving in adverse weather conditions 6 Encouraging motorcycle and bicycle awareness 4 Encouraging proper lane and shoulder use 3 Encouraging proper response around emergency vehicles 2 Discouraging drowsy driving 2 Encouraging use of turn signals 2 Encouraging car seat use and other child-passenger safety 1 Encouraging Share-the-Road driving behaviors 1 Encouraging safe driving during Back-to-School times 1 Other miscellaneous messages 4 Table 2. Distribution of safety topics used in BTS messages on VMS.

Current Practices Regarding BTS Message Design and Display on VMS 2-13   In terms of the length of BTS messages displayed on VMS, Table 3 shows that 55 percent of agencies limit such messages to what can be posted on a single VMS phase. The remaining 45 percent use a combination of single-phase and dual-phase BTS messages or two-phase BTS messages exclusively on their VMS. BTS messages displayed by agencies on VMS ranged in length from two to 20 words. As Table 4 demonstrates, 42 percent of the BTS messages reviewed used six words or fewer, and 41 percent of the messages used seven to nine words. The remaining 17 percent of BTS messages consisted of 10 or more words. Most of the BTS messages reviewed focused on a single safety topic. However, some messages addressed two safety topics (typically one per phase) whereas other messages displayed a specific safety message on one phase and basic safety information (e.g., number of fatalities, number of citations, a general “drive safely” message) or a travel time message on the second phase. Nearly 40 percent of the BTS messages reviewed used one or more special characters in the message, and nearly 14 percent utilized one or more sets of numbers. Punctuation marks were the most common type of character used, although a few messages utilized a hashtag to simulate a social media post or a special phone number. Many different types of numbers were used in the messages, including • Traffic fatality counts, • Phone numbers, • Number of citations or arrests, • Amount of potential fines, • Ages, • Children heights, • Durations (weeks, days, minutes), • Years and dates, • Distances, • Percentages, and • Number of passengers. Several agencies incorporated humor into BTS messages. According to social media posts as well as traditional media stories, many motorists perceive the use of humor in these messages positively. One recent study found that BTS messages utilizing humor elicit higher levels of Number of VMS Phases Used for BTS Messages Percent of Responding Agencies Single-phase BTS messages only 55 Both single-phase and dual-phase BTS messages 35 Dual-phase BTS messages only 10 Table 3. Number of VMS phases used for BTS messages. Number of Words Used Percent of All BTS Messages Reviewed 6 or fewer 42 7 to 9 41 10 or more 17 Table 4. Number of words used in BTS messages.

2-14 Behavioral Traffic Safety Messaging on Variable Message Signs brain activity than those that did not and concluded that such increased activity was indicative of higher message effectiveness (Shealy et al. 2020). However, as has been noted in the official FHWA official ruling as well as other behavioral traffic research, the use of humor can also create problems if the humor is not understood or offends someone (Kehrli 2021; Guttman 2015). As Table 5 shows, the three most common ways that agencies incorporated humor into BTS messages on VMS were to reference pop culture events, seasonal events, or icons in the message; to use some type of wordplay in the message (puns, the unusual spelling of words, etc.); or to incorporate a rhyme or jingle into the message. Of the BTS messages reviewed, nearly 30 per- cent utilized one or more of these techniques. Compliance with VMS Message Design Principles BTS messages were also critiqued with respect to their compliance with fundamental VMS message design principles outlined in the MUTCD and elsewhere. Overall, approximately 14 percent of the BTS messages reviewed had one or more characteristics that did not strictly conform to the MUTCD. Common nonconforming characteristics included the following: • Use of nonstandard abbreviations, particularly those attempting to replicate text messaging, such as #BUPD (which stands for “buckle up phones down”) that a few states have displayed or the example shown below. EXIT B4U TXT IT • Not designing each phase of the message as a complete thought to simplify understanding regardless of which phase is seen first, such as the following (note that the likely intended order of the message has been reversed to illustrate the issue). NOT SPEEDING TICKETS SPEND MONEY ON LOBSTERS • Ending one thought on a line and starting another thought on the same line, making it more difficult for motorists to comprehend the message. An example of this characteristic is shown here. YOUR FUTURE IS BRIGHT DON’T DRIVE DISTRACTED Message Characteristic Percent of All BTS Messages Reviewed References to pop culture 10 Use of wordplay 13 Use of rhymes or jingles 5 Total percent 28 Table 5. Use of wit, humor, or pop culture references in BTS messages.

Current Practices Regarding BTS Message Design and Display on VMS 2-15   Message Issue Percent of All BTS Messages Nonapproved abbreviations used 6 Message was confusing or unclear 4 Each VMS phase was not a complete thought 2 Message ended one thought and started a new one on the same line 2 Total percent of nonconforming BTS messages 14 Table 6. Relative frequency of VMS message design issues in BTS messages. • Displaying a message that is confusing to drivers or that does not easily indicate the traffic safety topic or desired action, such as the following. GREAT SCOTT! WATCH YOUR STEP, MCFLY! Table 6 summarizes the relative frequency of each of these message design issues. The use of nonstandard abbreviations was the most common, followed by messages that the research team could not easily understand overall or completely discern the traffic safety topic. It is important to note that some of the abbreviations were ones that most individuals would likely understand (i.e., DUI) or were punctuation symbols (i.e., “&” for “and”).

2-16 Introduction The task of driving places both cognitive and psychomotor demands on the driver. Drivers take information in from a variety of sources (the environment, traffic control devices, other vehicles), make decisions, and execute driving behaviors based on those decisions (accelerate, maintain current speed, brake, turn the steering wheel). These demands vary over time and distance based on both roadway and traffic conditions. The driving task itself requires a con- tinuous balancing act between attending to the needed or desired information that is available and attending to the proper control of the vehicle. If the combined demand for a driver’s atten- tion via the information sources and vehicle control requirements exceeds their capabilities to meet those demands, an overload situation occurs. Overload situations result in either degraded vehicular control performance or degraded perception and interpretation of the information. To investigate the extent to which BTS messages displayed on VMS can affect driver multi- tasking capabilities, the research team designed and conducted a laptop-based, human factors study utilizing a continuous secondary task activity while subjects were presented with various BTS messages. The study also included traffic management messages consisting of four units of information that served as a baseline for comparison to the BTS messages. Study Objectives The objectives of this laboratory study were as follows: • Determine whether the length of a BTS message (measured in terms of the total number of words used) adversely affects driver abilities to accomplish a secondary control task and/or their ability to effectively read and process the BTS message relative to driver abilities when viewing traffic management messages. • Determine whether the number and type of safety topics included in the message further affect those abilities. • Determine whether the use of humor, wit, or pop culture references also affects those abilities. • Determine whether the difficulty of the secondary control task affects those abilities. Study Methodology Critical Tracking Task Description Researchers used a critical tracking task (CTT) to create cognitive and psychomotor task demands on each test subject as the subject was presented with various VMS messages. Both BTS messages and four-unit traffic management messages were used in the study. If CTT C H A P T E R   7 Human Factors Testing of BTS Message Displays on VMS

Human Factors Testing of BTS Message Displays on VMS 2-17   performance while viewing any of the BTS messages was found to be worse than it was while viewing the baseline traffic management messages, it would suggest that the BTS message was creating potentially excessive attentional demands upon the driver. Similarly, if test subjects were found to be less able to identify the actual safety topic(s) of a BTS message than they were to identify an actual informational unit in the traffic management messages, it would suggest the BTS message did not reach an acceptable minimum level of VMS message understanding. Researchers hypothesized the subject’s ability to perform the CTT would vary as the difficulty of the task is increased and as BTS messages of different lengths and display characteristics are presented and formatted for VMS display. Simultaneously, increased CTT difficulty was expected to make it more difficult to effectively read and process the BTS messages under the limited viewing time afforded by VMS, which could affect driver understanding of the message presented. The CTT has been used in the automotive industry to assess driver distraction due to in-vehicle information systems (Petzoldt, Bellem, and Krems 2014) and has also been shown to correlate with subjective ratings of workload in research with airplane pilots (Rehmann, Stein, and Rosenberg 1983). The CTT used in this study required the subject to continuously keep a horizontal cursor line on a screen as close to a dashed centerline as possible throughout the test trial (Wagner and Weir 2006). Figure 12 illustrates the image viewed by subjects on one computer screen. The horizontal cursor was adjusted by subjects using a USB-attached joystick. Software parameter inputs defined how the cursor line moved up and down randomly from the centerline and how user inputs via the joystick controlled the cursor line. This allowed the research team to systematically control how difficult it was for a subject to keep the cursor line on or near the centerline. The software recorded the relative distance of the cursor line (normalized on a scale from 0 to 100) from the Figure 12. Screenshot of the CTT software tool showing the dashed red centerline target and the black cursor line manipulated by the subject using the joystick.

2-18 Behavioral Traffic Safety Messaging on Variable Message Signs centerline 50 times per second. The absolute values of these relative distances from the center- line were then averaged over the display time of the message to assess how well the subject performed the tracking task. The research team synchronized the computer running the CTT with a second computer and screen where the VMS messages were displayed. Messages were displayed for 8 seconds, simu- lating the typical amount of time that drivers have available to view and read a message while approaching and passing VMS. In this way, researchers were able to extract the CTT scores for each subject during the time that they were multitasking between attending to that task and reading the message. An 8-second period when the subject was performing the CTT immedi- ately preceding the display of each message was also extracted for use in the statistical analysis of the data. Figure 13 illustrates the study setup, showing the two computer displays that the subject monitored as well as the joystick used in the CTT. Researchers randomly assigned subjects to perform the study at either a low- or high-CTT level of difficulty. Once subjects received the required Institutional Review Board (IRB) infor- mation, they participated in a series of training trials to get familiar with the CTT operation. Difficulty parameters of the CTT were then established through a series of calibration trials. The subject responded after each trial with their assessment of the perceived CTT difficulty of that trial. Based on that feedback, the researchers assigned a CTT difficulty value corresponding to that subject’s self-reported, low- or high-difficulty level. That CTT value was used throughout the remainder of their study during the presentation of each of the messages. After each message was presented, the CTT was suspended while the subject responded to a series of questions to assess their understanding of the message and their opinion as to the likely effect of the message upon other drivers. • What was the safety topic of the message? (For the traffic management messages, the subject was asked a question about one of the units of information in the message.) • Did the message make sense to you? Figure 13. Example of the study setup for multitasking between the CTT control with the joystick and reading a BTS message.

Human Factors Testing of BTS Message Displays on VMS 2-19   • On a scale of 1 to 5, is the message likely to influence the behavior of other drivers (1 = not at all likely, 5 = extremely likely)? The research team assessed and recorded the subject’s response to the first question as either correct or incorrect for each phase of the message; recorded the subject’s response to the second question as either yes or no for each phase of the message; and for the third question, recorded the numerical value of the subject’s rating of the likely influence of the message on driving behavior. Subject Recruitment A total of 120 subjects (60 subjects per state) were recruited from locations in Texas (Austin and College Station) and Pennsylvania (Alexandria, Harrisburg, and Blue Bell). Subjects were balanced by gender uniformly across three age ranges (40 subjects per group): • ≤30 • 31–64 • ≥65 Researchers used social media postings, postings of flyers in some office buildings, and word- of-mouth recruitment by subjects themselves for the study. Special procedures were enacted because of the COVID-19 pandemic to protect the health of both the subjects and the researchers. Subjects were temperature-screened before entering the building for a study session and attested that they were not COVID-19 positive or had not recently been around anyone who had tested positive. All contact surfaces were disinfected before and after each subject participated in the study. Both researchers and subjects wore masks throughout the study. In addition, social dis- tancing was enforced during each study. Overall, the study took approximately 1 hour to com- plete per subject. Subjects were provided an electronic $50 gift card as compensation for their willingness to participate in the study. Experimental Design The experimental design for the study consisted of three main message design factors: two factors had three levels, and one factor had two levels. The factors and factor levels were selected based on the research team’s review of the actual BTS messages provided by the agencies. The factor levels were as follows: • Number of words in the BTS message: – 9 to 11 words. – 15 to 16 words. – 18 to 21 words. • Safety topic(s) of the message: – One safety topic repeated in each phase (different words on each). – Two different safety topics (one on each phase). – One safety topic and one general topic (a generic “drive safely” message, number of fatali- ties, number of citations issued, size of fines). • Use of humor, wit, or pop culture references in the message: – No. – Yes. Thus, the study required a total of 3 × 3 × 2 = 18 different BTS messages. All messages tested were designed as two-phase messages. Table 7, Table 8, and Table 9 present the 18 BTS messages used in the study. These messages were drawn from the sample of messages provided by agencies responding to the previously described survey conducted under this study.

2-20 Behavioral Traffic Safety Messaging on Variable Message Signs One Safety Topic Implied in Both Phases Phase 1 Phase 2 M1 SHARE THE ROAD WITH MOTORCYCLES WATCH FOR MOTORCYCLES, DRIVE SAFELY M2 NOBODY RELISHES A PICKLED DRIVER DON'T BE A TURKEY DRIVE SOBER Two Different Safety Topics Implied in Each Phase Phase 1 Phase 2 M3 DRIVE HIGH GET A DUI SLOW DOWN AND SAVE A LIFE M4 YAKETY YAK DON'T TEXT BACK TRICK OR TREAT NO LEAD FEET One Safety Topic in One Phase and One General Statement in Other Phase Phase 1 Phase 2 M5 SLOW DOWN ENJOY THE RIDE 1200 TRAFFIC DEATHS THIS YEAR M6 DON'T DRIVE INTEXTICATED BE SAFE DRIVE SMART FARMERS FIGHT M = message. Table 7. BTS test messages using 9 to 11 words. To establish the baseline of subject abilities when performing the CTT at either the low- or high-difficulty level (depending on the group to which they are assigned), a series of three traffic management messages pertaining to an incident, special event, or roadwork conditions were included in the study session. The traffic management messages all contained four units of information, the maximum that the MUTCD and VMS guidelines recommend. The traffic management messages also consisted of two phases, with two units of information presented in each phase. The traffic management messages are shown in Table 10. Ten different BTS and traffic management messages demonstrating presentation orders were then generated randomly to aid in counterbalancing any learning effects that might occur with the CTT or with viewing the messages. Results Average absolute CTT scores, percent correct identification of safety topic(s) of each BTS message (or a unit of information from each traffic management message), and subject self- assessments of their understanding of each message are provided in Appendix C. Considerable message-to-message differences are evident in those data. Analyses of these measures across key demographic and message design factors are presented herein.

Human Factors Testing of BTS Message Displays on VMS 2-21   One Safety Topic Implied in Both Phases Phase 1 Phase 2 M7 STATE LAW BUCKLE UP EVERYONE EVERY TIME BUCKLE UP: IT COULD MEAN LIFE OR DEATH M8 LIFE IN THE FAST LANE TAKE IT EASY TELL YOUR LEAD FOOT TO LIGHTEN UP Two Different Safety Topics Implied in Each Phase Phase 1 Phase 2 M9 DRIVE SMART TEXT LATER IT CAN WAIT MOVE OVER FOR RED, BLUE OR AMBER LIGHTS M10 LEAVE THE BUZZ FOR THE BEES DRIVE SOBER HORNS UP PHONES DOWN IT CAN WAIT One Safety Topic in One Phase and One General Statement in Other Phase Phase 1 Phase 2 M11 EYES ON ROAD HANDS ON WHEEL MIND ON DRIVING 2500 SPEEDING TICKETS ISSUED LAST MONTH M12 DON'T MAKE TWO CLOSE SHAVES GROOM AT HOME DRIVE WITH CARE SO WE ALL GET THERE M = message. Table 8. BTS test messages using 15 to 16 words. Effects of Demographic Variables Table 11 presents the above-referenced measures of effectiveness stratified by study location and CTT difficulty level. As expected, there are much higher average CTT scores (indicating poorer performance) for subjects assigned to the high CTT difficulty level than the scores for subjects assigned to the low CTT difficulty level. This indicates that participants were splitting their attention between the CTT and reading the messages as instructed. The effect of CTT dif- ficulty level was evident for both the BTS messages and the traffic management messages for all subjects, regardless of location. Average CTT scores tended to be higher for the BTS messages than for the traffic management messages, but not markedly. The subjects’ abilities to identify the safety topic(s) of the BTS messages or the information unit of interest in the traffic manage- ment messages were not consistently affected by the CTT difficulty level. However, relative to the traffic management messages, BTS messages resulted in substantially lower percentages of cor- rect safety topic identification or perceived understanding of the messages at both low and high CTT difficulty levels. Average CTT scores, as well as percentages of correct information unit and correct safety topic identification, were slightly lower for Texas subjects relative to Pennsylvania subjects, but again not markedly. Almost all subjects from both study locations indicated that they understood the traffic management messages, but somewhat greater percentages of Texas subjects indicated they understood the BTS messages than did the Pennsylvania subjects.

2-22 Behavioral Traffic Safety Messaging on Variable Message Signs One Safety Topic Implied in Both Phases Phase 1 Phase 2 M13 SLOW DOWN IN WORK ZONES, GIVE 'EM A BRAKE WORK ZONES - WE DON'T SPEED THROUGH YOUR OFFICE M14 SURELY YOU BUCKLE? YES I DO AND DON'T CALL ME SHIRLEY ALL YOU NEED IS LOVE…. AND A SEAT BELT Two Different Safety Topics Implied in Each Phase Phase 1 Phase 2 M15 IL LAW: USE REAR-FACING SEAT FOR KIDS UNDER 2 MOVE OVER A LANE OR SLOW DOWN FOR EMERGENCY VEHICLES M16 YOU'RE NOT THE BEST DRIVER IN THE GALAXY SLOW DOWN YEAH, IF YOU COULD NOT TEXT AND DRIVE THAT'D BE GREAT One Safety Topic in One Phase and One General Statement in Other Phase Phase 1 Phase 2 M17 MOVE OVER AND SLOW DOWN AT CRASH SCENES TRAVEL TIME TO I-10 8 MIN TO US-30 15 MIN M18 BABY YODA USES A CAR SEAT BE SAFE HE WILL THE RISE OF SAFE DRIVER TO END THE STREAK M = message. Table 9. BTS test messages using 18 to 21 words. Phase 1 Phase 2 I MAJOR ACCIDENT 3 MILES USE ALTERNATE ROUTES AVOID DELAYS SE STADIUM TRAFFIC USE BROAD ST EXIT THROUGH TRAFFIC USE LEFT LANE R ROADWORK 1 MILE LEFT LANE CLOSED EXPECT DELAYS I = incident; SE = special event; R = roadwork. Table 10. Traffic management messages to establish subject baseline performance.

Human Factors Testing of BTS Message Displays on VMS 2-23   Similar statistics by gender are presented in Table 12. Relative to the traffic management messages, BTS messages again resulted in significantly lower percentages of correct topic iden- tification or perceived understanding of the message relative to the traffic management mes- sages at both low- and high-CTT difficulty levels. Average CTT scores were slightly higher for the BTS messages relative to the traffic management messages. For both types of messages, female subjects on average had lower CTT scores than males at the low CTT difficulty level, but higher average scores at the high difficulty level. CTT difficulty level did not consistently affect the subjects’ abilities to identify the safety topic(s) of the BTS messages, whereas the high dif- ficulty level resulted in slightly lower percentages of correct identification of the information unit of interest in the traffic management messages. Table 13 presents results stratified by age category and CTT difficulty level. Average CTT scores increased as age and the CTT difficulty level increased. A subject’s ability to correctly identify the information unit of interest in the traffic management messages and the safety topic of the BTS messages also degraded as age increases. However, the subjects’ self-reported under- standing of the BTS messages was consistent across the three age groups but was lower overall than for the traffic management messages. Effects of BTS Message Design Factors The most prominent BTS message design factor affecting subject performance was the use of humor, wit, or pop culture references in the message. As Table 14 shows, the subjects’ abilities State CTT Difficulty Level Traffic Management Baseline Messages BTS Messages Avg. CTT Score (S.E.) % Correct Info Unit (S.E.) % Understood (S.E.) Avg. CTT Score (S.E.) % Correct Safety Topic (S.E.) % Understood (S.E.) PA Low 5.842(1.047) 92 (2.9) 100 (0) 6.299 (0.401) 72 (2.0) 70 (2.0) High 17.513(2.171) 85 (3.8) 99 (1.0) 19.934 (0.921) 76 (1.8) 66 (2.0) TX Low 5.662(1.249) 82 (4.1) 98 (1.5) 5.860 (0.436) 71 (1.9) 73 (1.9) High 14.981(1.844) 81 (4.0) 99 (1.0) 18.022 (0.849) 70 (2.0) 78 (1.8) NOTE: PA = Pennsylvania; TX = Texas; S.E. = standard error. Table 11. Effect of study location and CTT difficulty level on subject performance and responses. Table 12. Effect of gender and CTT difficulty level on subject performance and responses. Gender CTT Difficulty Level Traffic Management Baseline Messages BTS Messages Avg. CTT Score (S.E.) % Correct Info Unit (S.E.) % Understood (S.E.) Avg. CTT Score (S.E.) % Correct Safety Topic (S.E.) % Understood (S.E.) Female Low 4.422(0.976) 89 (3.3) 99 (1.0) 4.880 (0.391) 73 (1.9) 71 (2.0) High 18.320(2.156) 86 (3.6) 99 (1.0) 21.974 (0.972) 73 (1.9) 73 (1.9) Male Low 7.082(1.323) 86 (3.7) 99 (1.0) 7.280 (0.445) 71 (2.0) 72 (1.9) High 14.031(1.816) 80 (4.3) 99 (1.1) 15.775 (0.751) 73 (1.9) 70 (2.0) NOTE: S.E. = standard error.

2-24 Behavioral Traffic Safety Messaging on Variable Message Signs to correctly identify the safety topic(s) of a BTS message without humor, wit, or pop culture references were very similar to their abilities to identify an information unit of interest in traf- fic management messages. In addition, the subjects’ self-reported understanding of these types of BTS messages was only slightly lower than their self-reported understanding of the traffic management messages. However, when humor, wit, or pop culture references were included in the BTS messages, the subjects’ safety topic identification abilities and self-reported under- standing were significantly lower than those for the traffic management messages. Similarly, the average CTT scores for the BTS messages without humor, wit, or pop culture references were very similar to traffic management messages at both low and high CTT difficulty levels, whereas those of BTS messages with humor, wit, or pop culture references were significantly higher. If one further stratifies the average CTT scores for the BTS messages using humor, wit, or pop culture references by the subjects’ abilities to identify the safety topic(s) of the messages, it becomes apparent that the lack of understanding of such messages results in worse average CTT scores for the BTS messages compared with traffic management messages, as can be seen in Table 15. Age Group CTT Difficulty Level Traffic Management Baseline Messages BTS Messages Avg. CTT Score (S.E.) % Correct Info Unit (S.E.) % Understood (S.E.) Avg. CTT Score (S.E.) % Correct Safety Topic (S.E.) % Understood (S.E.) ≤30 Low 1.794(0.201) 93 (3.3) 100 (0) 3.135 (0.176) 76 (2.3) 71 (2.4) High 10.294 (1.685) 87 (4.3) 100 (0) 12.410 (0.679) 79 (2.1) 72 (2.4) 31–64 Low 6.006(1.424) 87 (4.3) 98 (1.8) 5.496 (0.446) 76 (2.3) 73 (2.3) High 14.505(2.182) 82 (4.6) 100 (0) 18.124 (1.035) 69 (2.4) 73 (2.3) ≥65 Low 9.456(1.907) 82 (5.0) 98 (1.87) 9.607 (0.715) 64 (2.5) 71 (2.4) High 23.941(3.031) 82 (5.0) 97 (2.2) 26.400 (1.316) 71 (2.4) 71 (2.4) NOTE: S.E. = standard error. Table 13. Effect of age and CTT difficulty level on subject performance and responses. Message Type CTT Difficulty Level Avg. CTT Score (S.E.) % Correct Info Unit (S.E.) % Correct Safety Topic (S.E.) % Understood (S.E.) Traffic management baseline messages Low 5.752(0.826) 87 (2.5) na 99 (0.7) High 16.247(1.423) 83 (2.8) na 99 (0.7) BTS messages without humor, wit, or pop culture references Low 5.553(0.372) na 87 (1.4) 91 (1.2) High 18.352(0.883) na 86 (1.5) 89 (1.3) BTS messages with humor, wit, or pop culture references Low 6.606(0.465) na 57 (2.1) 53 (2.1) High 19.604(0.889) na 61 (2.1) 54 (2.1) NOTE: S.E. = standard error; na = not applicable in these categories. Table 14. Effect of use of humor or pop culture references and CTT difficulty level on subjects’ performance and responses compared with traffic management messages.

Human Factors Testing of BTS Message Displays on VMS 2-25   The incorporation of humor, wit, and pop culture references into BTS messages also had a detrimental effect on subject ratings of the likelihood that the message would positively influ- ence the behavior of drivers. As shown in Table 16, subjects rated the traffic management mes- sages very high for this question, yielding an average 4.6 rating out of 5 and with 93 percent of subjects rating such messages as likely or very likely to influence driving behavior. In com- parison, BTS messages that included humor, wit, and pop culture references were rated much lower on average, especially if the subject was not able to correctly identify the safety topic of the message. Those subjects who were able to identify the safety topic of the BTS messages with humor, wit, and pop culture references only gave an average 2.7 rating to such messages, with only 26 percent of subjects giving likely or very likely ratings. Those subjects who could not correctly identify the safety topic of the BTS messages using humor, wit, and pop culture references rated such messages even lower on average (a 1.8 average rating out of 5), and only 13 percent of those subjects rated those messages as likely or very likely to influence driving behavior. Given the adverse effect of humor, wit, or pop culture references upon a subject’s abilities, the effects of message length, as well as number and type of safety topic(s) included in the BTS messages, were analyzed using only data from messages without humor, wit, or pop culture reference (see Table 17). At the low CTT difficulty level, average CTT scores and the percent of subjects correctly identifying the safety topic(s) of the BTS messages in the two lower message length categories (9 to 11 words and 15 to 16 words) were better than or comparable to values for the traffic management messages. However, BTS messages between 18 and 21 words in length resulted in a substantially higher average CTT score and lower percentages of subjects correctly identifying the safety topic(s) of the messages and self-reporting as understanding the BTS message. Average Rating (1= Not Likely, 5=Very Likely) % of Subjects Rating the Message As Likely or Very Likely to Influence Behavior Traffic management baseline messages 4.6 93 BTS Messages with Humor, Wit, or Pop Culture References If safety topic correctly interpreted 2.7 26 If safety topic not correctly interpreted 1.8 13 Table 16. Effect of use of humor, wit, or pop culture references in BTS messages upon perceptions of message abilities to influence driving behavior. Table 15. Effect of the subject’s ability to correctly interpret the safety topic(s) of a BTS message with humor upon CTT performance compared with traffic management messages. Message CTT Difficulty Level Low (S.E.) High (S.E.) Traffic management baseline messages 5.752(0.826) 16.247 (1.423) Subjects correctly interpret safety topic(s) of BTS messages using humor 5.101 (0.447) 15.851 (0.901) Subjects do not correctly interpret safety topic(s) of BTS messages using humor 8.604 (0.889) 25.366 (1.709) NOTE: S.E. = standard error.

2-26 Behavioral Traffic Safety Messaging on Variable Message Signs At the high CTT difficulty level, average CTT scores for BTS messages with greater than 11 words were moderately to substantially higher than for the traffic management messages. The percent of subjects correctly identifying the safety topic(s) of BTS messages of all lengths was comparable to the percent of subjects correctly identifying a unit of information in the traffic management messages. However, the percentage of subjects indicating that they understood the BTS messages of all lengths was lower than for the traffic management messages, most substantially so for the two higher message length categories. For both the low and high CTT difficulty levels, subject ratings of the likelihood that the messages would influence driving behavior were consistent across the three BTS message length categories. Average ratings of the BTS messages were lower than for the traffic management messages as were the percentages of subjects rating the messages as likely or very likely to influ- ence behavior. None of the message length categories received such ratings from more than 48 per- cent of the subjects. Next, Table 18 shows the effect of the number and type of topics in a BTS message without humor, wit, or pop culture references upon subject performance and responses. At both CTT difficulty levels, BTS messages displaying one safety topic on each VMS phase or a safety topic on one phase and generic information—safety statistics, travel time information, or a generic “drive safely” message—on the second phase resulted in average CTT scores that were not markedly higher than those for the traffic management messages. Similarly, the subjects’ abilities to identify the safety topic of the message and their self-assessment of message understanding were also comparable to those recorded for the traffic management messages. However, BTS messages displaying two different safety topics (one on each phase) resulted in higher average CTT CTT Difficulty Level Message Type Avg. CTT Score (S.E.) % Correct Info Unit (S.E.) % Correct Safety Topic (S.E.) % Understood (S.E.) Avg. Rating Likely to Change Behaviora Low Traffic management baseline messages 5.752 (0.826) 87 (2.5) na 99 (0.7) 4.6 (92) BTS messages: 9–11 words 4.544 (0.580) na 92 (2.1) 95 (1.6) 3.5 (44) BTS messages: 15–16 words 5.588 (0.681) na 91 (2.2) 92 (2.0) 3.3 (34) BTS messages: 18–21 words 6.528 (0.663) na 78 (3.1) 86 (2.6) 3.6 (48) High Traffic management 16.247 (1.423) 83 (2.8) na 99 (0.7) 4.6 (93)baseline messages BTS messages: 9–11 words 13.358 (1.255) na 88 (2.4) 93 (1.9) 3.3 (36) BTS messages: 15–16 words 19.618 (1.634) na 89 (2.3) 91 (2.2) 3.3 (33) BTS messages: 18–21 words 22.081 (1.605) na 80 (3.0) 84 (2.7) 3.5 (45) NOTE: S.E. = standard error; na = not applicable in these categories. aAverage rating where 1 = Not Likely and 5 = Extremely Likely (percent of subjects rating as “Likely” or “Very Likely”) Table 17. Effect of CTT difficulty level and message length (without humor, wit, or pop culture references) on subject performance and responses compared with traffic management messages.

Human Factors Testing of BTS Message Displays on VMS 2-27   scores, lower abilities to correctly identify those topics, and lower self-assessments of message understanding. Subject ratings of the likelihood that the BTS messages would influence driving behaviors were lower than those of the traffic management messages but were similar among the three BTS message topic categories themselves at both CTT difficulty levels. Summary To summarize, using humor, wit, and pop culture references in a BTS message increased the percentage of subjects not correctly perceiving the safety topic(s) in the message. For those subjects, this lack of understanding or proper interpretation of the message adversely affected their ability to simultaneously perform a secondary task requiring both visual attention and use of fine motor skills. Given that driving in general also involves visual multitasking and the use of fine motor skills while viewing VMS messages, these results imply that displaying BTS messages involving humor, wit, or pop culture references could have adverse consequences on driving behavior for motorists who are unable to correctly interpret those messages. Table 18. Effect of CTT difficulty and number of safety topics in messages (without humor, wit, or pop culture references) on subject performance and responses compared with traffic management messages. CTT Difficulty Level Message Type CTT Score (S.E.) % Correct Info Unit (S.E.) % Correct Safety Topic (S.E.) % Understood (S.E.) Likely to Change Behavior?a Low Traffic management baseline messages 5.752 (0.826) 87 (2.5) na 99 (0.7) 4.6 (92) 5.431 (0.670) na 96 (1.4) 97 (1.3) 3.5 (47) BTS messages with one safety topic on each phase BTS messages with two different safety topics (one on each phase) 6.362 (0.729) na 81 (2.9) 84 (2.7) 3.4 (41) BTS messages with one safety topic and one generic phase 4.867 (0.513) na 83 (2.8) 92 (2.1) 3.4 (39) High Traffic management baseline messages 16.247 (1.423) 83 (2.8) na 99 (0.7) 4.6 (93) BTS messages with one safety topic on each phase 17.993 (1.430) na 99 (0.8) 97 (1.2) 3.3 (50) BTS messages with two different safety topics (one on each phase) 19.386 (1.714) na 73 (3.3) 77 (3.1) 3.3 (28) BTS messages with one safety topic and one generic phase 17.678 (1.433) na 86 (2.6) 93 (1.9) 3.5 (36) NOTE: S.E. = standard error; na = not applicable in these categories. aAverage rating where 1 = Not Likely and 5 = Extremely Likely (% of subjects rating as “Likely” or “Very Likely”) Avg.

2-28 Behavioral Traffic Safety Messaging on Variable Message Signs For BTS messages without humor, wit, or pop culture references, this study also indicated that messages greater than 16 words resulted in worse CTT scores, a lower percent of correct iden- tification of safety topics, and a lower percent of self-reported understanding of the messages than when subjects viewed traffic management messages with four information units (the maximum recommended length of traffic management messages). At high CTT difficulty levels, even the 15-to-16-word BTS messages had somewhat higher CTT scores and lower percentages of self-reported understanding of the messages relative to the traffic management messages. Finally, BTS messages that addressed two different safety topics (one in each phase of the message) resulted in higher CTT scores, lower percentages of correct identification of the safety topics, and lower percentages of self-reported understanding of the messages relative to the traffic management messages. These results were consistent across both the low and high CTT difficulty levels.

2-29   Conclusions The objective of this research project was to develop a guide for the use of VMS to deliver BTS messages to motorists. The project consisted of a thorough review of U.S. and international lit- erature on the topic; collection, collation, and analysis of BTS messages that have been displayed on VMS across the country as well as the processes used to develop and display those mes- sages; and a computer-based laboratory study designed to aid the research team in determining acceptable BTS message design parameters for display on VMS. Regardless of the dissemination mechanism being used, effective BTS messages are cred- ible, trustworthy, consistent, clear, persuasive, relevant, and appealing to the target audience. BTS messages can present a “gain” to be had by avoiding some behavior or by adopting a safer behavior or a “loss” to be experienced by engaging in the undesirable behavior or failing to adopt the safer behavior. The literature indicates that gain-framed messages tend to be more effective than loss-framed messages, although there are examples where loss-framed messages have had the desired effect on drivers. Males tend to be less influenced by negative, loss-framed messages than females. Instead, the use of humor in BTS messages appears to be more effec- tive in influencing males. However, excessively humorous BTS messages may entertain those viewing the message without getting them to accept or understand the safety analogy being presented. Furthermore, humor and pop culture references need to be familiar and liked by the target drivers to be effective. BTS messages displayed on VMS must also comply with basic human factors and traf- fic engineering principles regarding VMS message design. Drivers have limited viewing time as they approach VMS during which a message is legible. During this viewing time, drivers must multitask between viewing the VMS in brief glimpses, scanning the roadway environment, monitoring vehicle displays, and controlling the vehicle. BTS messages must not be too long or confusing and must be formatted properly to facilitate quick and correct interpretation. It is also important to remember that VMS are traffic control devices, and as such, messages displayed on them should conform to the traffic control device principles outlined in the MUTCD. FHWA has also issued an official ruling that addresses the display of BTS messages on VMS. Key points from that ruling include the following: • BTS messages on VMS should supplement a larger roadway safety campaign and be coordi- nated with enforcement efforts. • BTS messages should be tailored to the safety issues experienced on the type of roadway where the message is being displayed. • BTS messages suggested by the public should be revised as needed to meet acceptable VMS message design criteria. C H A P T E R   8 Conclusions and Recommendations

2-30 Behavioral Traffic Safety Messaging on Variable Message Signs • Use of humor, wit, colloquialisms, and pop culture references should be avoided in BTS messages. • Use of websites, domain names, hashtags, or electronic device application names in the message should also be avoided. • Scrolling lines, animation, flashing displays, punctuation, and nonapproved symbols should not be used in BTS messages (or any VMS message). The information provided in the MUTCD and the FHWA official ruling, however, did not address what constitutes acceptable BTS message design criteria for display on VMS. For example, should BTS message length be limited to a maximum number of words? Is it acceptable to pre- sent more than one traffic safety topic in VMS messages (such as seat belt use and no cell phone use) or to combine a BTS message with a travel time or other general message? Is the incorpora- tion of humor, wit, or pop culture references actually detrimental to BTS messages displayed on VMS? Although discouraged in the FHWA official ruling, several agencies have received positive feedback from the public about humorous BTS messages they have displayed on VMS in the past. To address these questions, a laptop-based laboratory study was developed and performed in Texas and Pennsylvania. The study presented subjects with BTS messages that varied in length, number and types of safety topics, and use of humor, wit, or pop culture references. Study results indicated that a significant proportion of drivers did not understand the safety topics of BTS messages that included humor, wit, or pop culture references. More importantly, those drivers who did not understand the safety topic(s) of BTS messages using humor or pop culture references did significantly worse on the CTT while viewing the message than did those drivers who understood the message. Study results also indicated that even for BTS messages not using humor, wit, or pop culture references, longer messages and messages displaying two different safety topics (one on each phase of a two-phase message) resulted in higher CTT scores, lower percentages of correct safety topic identification, and lower percentages of self-reported under- standing of the messages than when viewing four-unit, traffic management messages. Recommendations Based on the results of this research, it is recommended that • BTS messages to be displayed on VMS not include humor, wit, or pop culture references in the message. • Total length of BTS messages displayed on VMS be limited to no more than 16 words or numbers. • BTS messages be limited to no more than 11 words or numbers at locations and during time periods when driver workload is high. • BTS messages address only a single safety topic or a single safety topic on one phase and gen- eral information (travel times, generic “drive safely” message) on the second phase as long as the 16-word or number limit is not exceeded. Furthermore, it is recommended that BTS messages be designed according to the following principles of good VMS message design. • Messages should be limited to no more than two VMS phases. • Messages should be tailored to the types of safety issues that occur on the type of roadway where the VMS are located. • Messages should not include websites, domain names, hashtags, or electronic device applica- tion names.

Conclusions and Recommendations 2-31   • Messages should not include telephone numbers. • Messages should not include scrolling lines, animation, flashing displays, punctuation, or graphic symbols or icons not included in the MUTCD. • Each phase of a two-phase VMS message should be understandable by itself regardless of the order in which the phases are viewed. • BTS message thoughts or phrases should not be split between two VMS phases. • Each line of a message should be centered on the VMS. • Each new thought in the message should start on a new line on the VMS. • Nonstandard or texting abbreviations should not be used in a BTS message displayed on VMS. Although outside of the scope of this study, the literature review indicated mixed results from other studies that have attempted to evaluate the effectiveness of BTS messages displayed on VMS on driving behavior. It is recommended that additional studies be designed and conducted to determine which BTS topics are most effective at reducing undesirable driver behaviors and traffic crashes.

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2-34 Behavioral Traffic Safety Messaging on Variable Message Signs Robertson, R.D. and C.R. Pashley. 2015. Road Safety Campaigns: What the Research Tells Us. Canadian Auto- mobile Association and the Traffic Injury Research Foundation, Ottawa, Ontario. Rodier, C., R.S. Finson, J. Lidicker, and S.A. Shaheen. 2010. An Evaluation of the Consequences and Effectiveness of Using Highway Changeable Message Signs for Safety Campaigns. Report No. UCF-ITS-PRR-2010-3. Institute of Transportation Studies, University of California-Berkeley. Rogers, R.W. 1975. A Protection Motivation Theory of Fear Appeals and Attitude Change. The Journal of Psy- chology, Volume 91, Issue 1, 1975, pp. 93–114. Rosenstock, I.M. 1974. The Health Belief Model and Preventive Health Behavior. Health Education Monographs, Volume 2, Issue 4, December 1974, pp. 354–386. Schramm, A.J., A. Rakotonirainy, S.S. Smith, I.M. Lewis, D.W. Soole, B.C. Watson, and R.J. Troutbeck. 2012. Effects of Speeding and Headway-Related Variable Message Signs on Driver Behavior and Attitudes. Depart- ment of Transport and Main Roads, Brisbane, Australia. Schroeder, J.L. and M.J. Demetsky. 2010. Evaluation of Driver Reactions for Effective Use of Dynamic Message Signs in Richmond, Virginia. Report No. FHWA/VTRC 10-R16. Virginia Transportation Research Council, Charlottesville, VA. Schroeder, J., E. Plapper, H. Zeng, and B. Krile. 2016. Public Perception of Safety Messages and Public Service Announcements on Dynamic Message Signs in Rural Areas. Report No. FHWA-HOP-16-048. FHWA, U.S. Department of Transportation, Washington, DC. Shealy, T., P. Kryschtal, K. Franczek, and B.J. Katz. 2020. Driver Response to Dynamic Message Sign Safety Campaign Messages. Report No. FHWA/VRTRC 20-R16. Virginia Transportation Research Council, Charlottesville, VA. Tay, R. and A. Debarros. 2008. Public Perceptions of the Use of Dynamic Message Signs. Journal of Advanced Transportation, Volume 42, Issue 1, January 2008, pp. 95–110. Tay, R. and A. Debarros. 2010. Effectiveness of Road Safety Messages on Variable Message Signs. Journal of Transportation Systems Engineering and Information Technology, Volume 10, Issue 3, June 2010, pp. 18–23. Triandis, H. 1977. Interpersonal Behavior. Brooks/Cole, Monterey, CA. Wagner, R.C. and D.H. Weir. 2006. Software Users Guide for the Critical Tracking Task (CTT). Report No. DRI- TM-140-4. Dynamic Research, Inc., Torrance, CA. Wilson, T.D., S. Lindsay, and T.Y. Schooler. 2000. A Model of Dual Attitudes. Psychological Review, Volume 1, No. 1, January 2000, pp. 101–126.

B-1   A P P E N D I X B Agency Survey Questions 1. Which Transportation Management Centers (TMCs)/Traffic Operations Centers (TOCs) in your jurisdiction display BTS messages on your variable message signs (VMS), also referred to as changeable message signs (CMS) and dynamic message signs (DMS)? Could you provide contact information for managers at those TMCs/TOCs that we could interview as well about their practices and experiences? 2. Does your agency develop BTS messages to display on your VMS? Are TMCs permitted to create their own messages, or are they limited only to messages approved by headquarters? (If the latter, also need to go through questions below with TMC staff in those agencies.) Do you have a team or task force that comes up with messages? (If so, please share the names and position titles of those on the team/task force.) o If you are not involved in the development process, please identify the individual(s) we should contact about your procedures. How often does the team/task force meet/communicate? If your agency has a written policy or procedure on how you create and approve BTS messages you will display, please provide. Please provide information on the following topics if they are not covered in the policy or procedure… How are the ideas/messages generated? Do you solicit public input for ideas? How do you decide whether or not to use a message idea (either one created by agency staff or by the public)? What is the maximum length of message you allow? What message formatting requirements (if any) do you follow? When abbreviating words, does your agency work from an approved list of abbreviations? What restrictions on topics to be used do you follow? Please share examples of any message ideas that you rejected and why they were rejected.     

B-2 Behavioral Traffic Safety Messaging on Variable Message Signs g. Do you use BTS messages from other agencies? How do you find out about those messages? h. Do you display different BTS messages on different VMS at the same time? If so, how often do you do this? i. Do you have any full-color VMS? If so, have you displayed any BTS messages that used different colors? If so, please provide. j. Have you displayed any BTS messages that included graphics or used different font characteristics in the messages (words bolded, larger font, etc.)? If so, please provide. k. Have you displayed any BTS messages that flash any or part of the message? If so, please provide. l. Do you post BTS messages on any portable changeable message signs (PCMS) in your jurisdiction?  If so, do they differ from those posted on your permanent VMS?  Could you provide a library of BTS messages you have displayed on your PCMS? Have there been media stories regarding your messages? Have you received any unsolicited compliments from the public about any of the messages? If so, could you provide examples of the messages and comments received about them? Have you received any unsolicited complaints from the public about any of the messages? If so, could you provide examples of the messages and comments received about them? 3. Do you display BTS messages on your VMS? If possible, please provide a list or file of BTS messages you have displayed on VMS and/or are planning to display in the future. If you have a written policy or procedure on how you decide when, where, and how long you display messages on VMS, please provide. a. How often do you display BTS messages? Is there a daily, weekly, or seasonal schedule you use to display messages? (If so, please provide.) b. Do TMC managers/staff decide when and where to display BTS messages, or is it mandated at headquarters? c. Do you display BTS messages on all of the VMS in your jurisdiction, or only on certain VMS? If the latter, how do you decide which VMS to display or not display BTS messages? d. How long do you display a particular message? e. What priority level is given to BTS messages, relative to other message types you display on your VMS? f. Do you recycle BTS messages to display? If so, how much time do you wait before reusing a message? (Primarily for TMC staff): Have you or your operators observed any traffic operational or safety issues when a particular BTS message was displayed? If so, could you provide the message that was used, and describe the problem that you observed? Were there unique roadway or traffic characteristics that contributed to the issues (please describe)? 4. Does your agency have any questions or issues it is wrestling with regarding the creation and display of BTS messages on VMS? 5. Has your agency undertaken any specific evaluations of the effects of the BTS messages displayed on VMS? If so, could we obtain a copy of the evaluation results?      

C-1   A P P E N D I X C Raw Human Factors Study Results Figure C-1. Subject understanding BTS message safety topics using 9 to 11 words by age group. Phase 1 Topic Correct? Phase 2 Topic Correct? Age % Correct Age % Correct M1 SHARE THE ROAD WITH MOTORCYCLES ≤ 30 100 WATCH FOR MOTORCYCLES DRIVE SAFELY ≤ 30 100 31-64 100 31-64 100 65+ 100 65+ 95 Average 100 Average 98 M2 NOBODY RELISHES A PICKLED DRIVER ≤ 30 63 DON'T BE A TURKEY DRIVE SOBER ≤ 30 83 31-64 88 31-64 90 65+ 83 65+ 80 Average 78 Average 84 M3 DRIVE HIGH GET A DUI ≤ 30 100 SLOW DOWN AND SAVE A LIFE ≤ 30 93 31-64 98 31-64 80 65+ 98 65+ 75 Average 98 Average 83 M4 YAKETY YAK DON'T TEXT BACK ≤ 30 93 TRICK OR TREAT NO LEAD FEET ≤ 30 75 31-64 98 31-64 78 65+ 85 65+ 60 Average 92 Average 71 M5 SLOW DOWN ENJOY THE RIDE ≤ 30 93 1200 TRAFFIC DEATHS THIS YEAR ≤ 30 98 31-64 95 31-64 100 65+ 93 65+ 90 Average 93 Average 96 M6 DON'T DRIVE INTEXTICATED ≤ 30 70 BE SAFE DRIVE SMART FARMERS FIGHT ≤ 30 40 31-64 78 31-64 23 65+ 60 65+ 30 Average 69 Average 31 M = message.

C-2 Behavioral Traffic Safety Messaging on Variable Message Signs Figure C-2. Subject understanding BTS message safety topics using 15 to 16 words by age group. Phase 1 Topic Correct? Phase 2 Topic Correct? Age % Correct Age % Correct M7 STATE LAW BUCKLE UP EVERYONE EVERY TIME ≤ 30 100 BUCKLE UP: IT COULD MEAN LIFE OR DEATH ≤ 30 100 31-64 100 31-64 100 65+ 98 65+ 98 Average 99 Average 99 M8 LIFE IN THE FAST LANE TAKE IT EASY ≤ 30 95 TELL YOUR LEAD FOOT TO LIGHTEN UP ≤ 30 98 31-64 95 31-64 95 65+ 85 65+ 80 Average 92 Average 91 M9 DRIVE SMART TEXT LATER IT CAN WAIT ≤ 30 93 MOVE OVER FOR RED, BLUE OR AMBER LIGHTS ≤ 30 93 31-64 90 31-64 95 65+ 90 65+ 93 Average 91 Average 93 M10 LEAVE THE BUZZ FOR THE BEES DRIVE SOBER ≤ 30 90 HORNS UP PHONES DOWN IT CAN WAIT ≤ 30 88 31-64 85 31-64 80 65+ 75 65+ 60 Average 83 Average 76 M11 EYES ON ROAD HANDS ON WHEEL MIND ON DRIVING ≤ 30 100 2500 SPEEDING TICKETS ISSUED LAST MONTH ≤ 30 98 31-64 93 31-64 83 65+ 88 65+ 90 Average 93 Average 90 M12 DON'T MAKE TWO CLOSE SHAVES GROOM AT HOME ≤ 30 58 DRIVE WITH CARE SO WE ALL GET THERE ≤ 30 75 31-64 55 31-64 75 65+ 48 65+ 70 Average 53 Average 73 M = message.

Raw Human Factors Study Results C-3   Figure C-3. Subject understanding BTS message safety topics using 18 to 21 words by age group. Phase 1 Topic Correct? Phase 2 Topic Correct? Age % Correct Age % Correct M13 SLOW DOWN IN WORK ZONES, GIVE 'EM A BRAKE ≤ 30 100 WORK ZONES - WE DON'T SPEED THROUGH YOUR OFFICE ≤ 30 98 31-64 100 31-64 95 65+ 98 65+ 95 Average 99 Average 96 M14 SURELY YOU BUCKLE? YES I DO AND DON'T CALL ME SHIRLEY ≤ 30 93 ALL YOU NEED IS LOVE…. AND A SEAT BELT ≤ 30 98 31-64 85 31-64 83 65+ 85 65+ 88 Average 88 Average 89 M15 IL LAW: USE REAR-FACING SEAT FOR KIDS UNDER 2 ≤ 30 88 MOVE OVER A LANE OR SLOW DOWN FOR EMERGENCY VEHICLES ≤ 30 70 31-64 93 31-64 73 65+ 85 65+ 60 Average 88 Average 68 M16 YOU'RE NOT THE BEST DRIVER IN THE GALAXY SLOW DOWN ≤ 30 83 YEAH, IF YOU COULD NOT TEXT AND DRIVE THAT'D BE GREAT ≤ 30 83 31-64 70 31-64 75 65+ 65 65+ 78 Average 73 Average 78 M17 MOVE OVER AND SLOW DOWN AT CRASH SCENES ≤ 30 80 TRAVEL TIME TO I-10 8 MIN TO US-30 15 MIN ≤ 30 95 31-64 83 31-64 88 65+ 88 65+ 90 Average 83 Average 91 M18 BABY YODA USES A CAR SEAT BE SAFE HE WILL ≤ 30 85 THE RISE OF SAFE DRIVER TO END THE STREAK ≤ 30 53 31-64 88 31-64 35 65+ 70 65+ 35 Average 81 Average 41 M = message.

C-4 Behavioral Traffic Safety Messaging on Variable Message Signs Figure C-4. Subject self-reported understanding of BTS message using 9 to 11 words by age group. Phase 1 Message Phase Understood? Phase 2 Message Phase Understood? Age % Correct Age % Correct M1 SHARE THE ROAD WITH MOTORCYCLES ≤ 30 100 WATCH FOR MOTORCYCLES DRIVE SAFELY ≤ 30 100 31-64 98 31-64 100 65+ 100 65+ 100 Average 99 Average 100 M2 NOBODY RELISHES A PICKLED DRIVER ≤ 30 50 DON'T BE A TURKEY DRIVE SOBER ≤ 30 75 31-64 78 31-64 88 65+ 75 65+ 75 Average 68 Average 79 M3 DRIVE HIGH GET A DUI ≤ 30 100 SLOW DOWN AND SAVE A LIFE ≤ 30 95 31-64 98 31-64 98 65+ 98 65+ 85 Average 98 Average 93 M4 YAKETY YAK DON'T TEXT BACK ≤ 30 80 TRICK OR TREAT NO LEAD FEET ≤ 30 78 31-64 98 31-64 78 65+ 85 65+ 78 Average 88 Average 78 M5 SLOW DOWN ENJOY THE RIDE ≤ 30 90 1200 TRAFFIC DEATHS THIS YEAR ≤ 30 95 31-64 98 31-64 98 65+ 95 65+ 98 Average 94 Average 97 M6 DON'T DRIVE INTEXTICATED ≤ 30 60 BE SAFE DRIVE SMART FARMERS FIGHT ≤ 30 20 31-64 68 31-64 20 65+ 70 65+ 28 Average 66 Average 23 M = message.

Raw Human Factors Study Results C-5   Figure C-5. Subject self-reported understanding of BTS message using 15 to 16 words by age group. Phase 1 Message Phase Understood? Phase 2 Message Phase Understood? Age % Correct Age % Correct M7 STATE LAW BUCKLE UP EVERYONE EVERY TIME ≤ 30 100 BUCKLE UP: IT COULD MEAN LIFE OR DEATH ≤ 30 100 31-64 100 31-64 100 65+ 98 65+ 95 Average 99 Average 98 M8 LIFE IN THE FAST LANE TAKE IT EASY ≤ 30 83 TELL YOUR LEAD FOOT TO LIGHTEN UP ≤ 30 93 31-64 93 31-64 98 65+ 80 65+ 80 Average 84 Average 90 M9 DRIVE SMART TEXT LATER IT CAN WAIT ≤ 30 95 MOVE OVER FOR RED, BLUE OR AMBER LIGHTS ≤ 30 90 31-64 93 31-64 95 65+ 93 65+ 98 Average 93 Average 94 M10 LEAVE THE BUZZ FOR THE BEES DRIVE SOBER ≤ 30 88 HORNS UP PHONES DOWN IT CAN WAIT ≤ 30 68 31-64 90 31-64 63 65+ 88 65+ 60 Average 88 Average 63 M11 EYES ON ROAD HANDS ON WHEEL MIND ON DRIVING ≤ 30 95 2500 SPEEDING TICKETS ISSUED LAST MONTH ≤ 30 98 31-64 95 31-64 88 65+ 98 65+ 93 Average 96 Average 93 M12 DON'T MAKE TWO CLOSE SHAVES GROOM AT HOME ≤ 30 38 DRIVE WITH CARE SO WE ALL GET THERE ≤ 30 75 31-64 55 31-64 70 65+ 55 65+ 73 Average 49 Average 73 M = message.

C-6 Behavioral Traffic Safety Messaging on Variable Message Signs Figure C-6. Subject self-reported understanding of BTS message using 18 to 21 words by age group. Phase 1 Message Phase Understood? Phase 2 Message Phase Understood? Age % Correct Age % Correct M13 SLOW DOWN IN WORK ZONES, GIVE 'EM A BRAKE ≤ 30 100 WORK ZONES - WE DON'T SPEED THROUGH YOUR OFFICE ≤ 30 98 31-64 100 31-64 93 65+ 95 65+ 93 Average 98 Average 94 M14 SURELY YOU BUCKLE? YES I DO AND DON'T CALL ME SHIRLEY ≤ 30 78 ALL YOU NEED IS LOVE…. AND A SEAT BELT ≤ 30 98 31-64 78 31-64 93 65+ 63 65+ 93 Average 73 Average 94 M15 IL LAW: USE REAR-FACING SEAT FOR KIDS UNDER 2 ≤ 30 75 MOVE OVER A LANE OR SLOW DOWN FOR EMERGENCY VEHICLES ≤ 30 73 31-64 90 31-64 80 65+ 85 65+ 73 Average 83 Average 75 M16 YOU'RE NOT THE BEST DRIVER IN THE GALAXY SLOW DOWN ≤ 30 78 YEAH, IF YOU COULD NOT TEXT AND DRIVE THAT'D BE GREAT ≤ 30 82 31-64 73 31-64 78 65+ 78 65+ 73 Average 76 Average 78 M17 MOVE OVER AND SLOW DOWN AT CRASH SCENES ≤ 30 98 TRAVEL TIME TO I-10 8 MIN TO US-30 15 MIN ≤ 30 100 31-64 98 31-64 98 65+ 100 65+ 98 Average 98 Average 98 M18 BABY YODA USES A CAR SEAT BE SAFE HE WILL ≤ 30 78 THE RISE OF SAFE DRIVER TO END THE STREAK ≤ 30 35 31-64 73 31-64 20 65+ 58 65+ 33 Average 69 Average 29 M = message.

Raw Human Factors Study Results C-7   Figure C-7. Subject self-reported understanding of traffic management message topics by age group. Phase 1 Message Phase Understood? Phase 2 Message Phase Understood? Age % Correct Age % Correct I MAJOR ACCIDENT 3 MILES ≤ 30 100 USE ALTERNATE ROUTES AVOID DELAYS ≤ 30 100 31-64 100 31-64 100 65+ 100 65+ 100 Average 100 Average 100 SE STADIUM TRAFFIC USE BROAD ST EXIT ≤ 30 100 THROUGH TRAFFIC USE LEFT LANE ≤ 30 100 31-64 100 31-64 100 65+ 100 65+ 98 Average 100 Average 99 R ROADWORK 1 MILE ≤ 30 100 LEFT LANE CLOSED EXPECT DELAYS ≤ 30 100 31-64 100 31-64 98 65+ 100 65+ 95 Average 100 Average 98 O ve ra ll ≤ 30 100 ≤ 30 100 31-64 100 31-64 99 65+ 100 65+ 98 Average 100 Average 99 I = incident; SE = special event; R = roadwork.

C-8 Behavioral Traffic Safety Messaging on Variable Message Signs Figure C-8. Average CTT scores for BTS messages using 9 to 11 words by age group and self-determined CTT difficulty level. Message A ge D iffi cu lty A ve . Sc or e Message A ge D iffi cu lty A ve . S co re M 1 SHARE THE ROAD WITH MOTORCYCLES ≤ 30 L 2.103 M 2 NOBODY RELISHES A PICKLED DRIVER ≤ 30 L 2.999 H 9.358 H 11.056 31-64 L 3.853 31-64 L 5.832 WATCH FOR MOTORCYCLES DRIVE SAFELY H 12.892 DON'T BE A TURKEY DRIVE SOBER H 14.953 65+ L 7.786 65+ L 11.352 H 23.922 H 25.590 M 3 DRIVE HIGH GET A DUI ≤ 30 L 2.106 M 4 YAKETY YAK DON'T TEXT BACK ≤ 30 L 2.216 H 6.817 H 10.988 31-64 L 3.206 31-64 L 6.284 SLOW DOWN AND SAVE A LIFE H 10.953 TRICK OR TREAT NO LEAD FEET H 19.461 65+ L 9.579 65+ L 5.234 H 21.000 H 20.563 M 5 SLOW DOWN ENJOY THE RIDE ≤ 30 L 2.900 M 6 DON'T DRIVE INTEXTICATED ≤ 30 L 2.606 H 6.524 H 13.608 31-64 L 4.431 31-64 L 6.109 1200 TRAFFIC DEATHS THIS YEAR H 10.265 BE SAFE DRIVE SMART FARMERS FIGHT H 24.038 65+ L 4.937 65+ L 11.799 H 19.198 H 29.632 M = message.

Raw Human Factors Study Results C-9   Figure C-9. Average CTT scores for BTS messages using 15 to 16 words by age group and self-determined CTT difficulty level. Message A ge D iffi cu lty A ve . Sc or e Message A ge D iffi cu lty A ve . S co re M 7 STATE LAW BUCKLE UP EVERYONE EVERY TIME ≤ 30 L 3.117 M 8 LIFE IN THE FAST LANE TAKE IT EASY ≤ 30 L 2.100 H 15.524 H 13.301 31-64 L 4.451 31-64 L 5.084 BUCKLE UP: IT COULD MEAN LIFE OR DEATH H 19.770 TELL YOUR LEAD FOOT TO LIGHTEN UP H 16.282 65+ L 10.730 65+ L 11.326 H 24.532 H 31.837 M 9 DRIVE SMART TEXT LATER IT CAN WAIT ≤ 30 L 3.051 M 10 LEAVE THE BUZZ FOR THE BEES DRIVE SOBER ≤ 30 L 3.147 H 16.727 H 8.487 31-64 L 6.621 31-64 L 3.718 MOVE OVER FOR RED, BLUE OR AMBER LIGHTS H 11.368 HORNS UP PHONES DOWN IT CAN WAIT H 16.743 65+ L 7.752 65+ L 9.327 H 31.266 H 21.432 M 11 EYES ON ROAD HANDS ON WHEEL MIND ON DRIVING ≤ 30 L 1.969 M 12 DON'T MAKE TWO CLOSE SHAVES GROOM AT HOME ≤ 30 L 6.277 H 13.734 H 16.717 31-64 L 4.790 31-64 L 6.656 2500 SPEEDING TICKETS ISSUED LAST MONTH H 19.905 DRIVE WITH CARE SO WE ALL GET THERE H 29.820 65+ L 7.810 65+ L 11.132 H 25.736 H 26.936 M = message.

C-10 Behavioral Traffic Safety Messaging on Variable Message Signs Figure C-10. Average CTT scores for BTS messages using 18 to 21 words by age group and self-determined CTT difficulty level. Message A ge D iffi cu lty A ve . Sc or e Message A ge D iffi cu lty A ve . S co re M 13 SLOW DOWN IN WORK ZONES, GIVE 'EM A BRAKE ≤ 30 L 2.306 M 14 SURELY YOU BUCKLE? YES I DO AND DON'T CALL ME SHIRLEY ≤ 30 L 3.261 H 9.484 H 10.090 31-64 L 5.879 31-64 L 5.261 WORK ZONES - WE DON'T SPEED THROUGH YOUR OFFICE H 20.712 ALL YOU NEED IS LOVE…. AND A SEAT BELT H 19.846 65+ L 8.656 65+ L 12.584 H 25.747 H 28.860 M 15 IL LAW: USE REAR-FACING SEAT FOR KIDS UNDER 2 ≤ 30 L 5.897 M 16 YOU'RE NOT THE BEST DRIVER IN THE GALAXY SLOW DOWN ≤ 30 L 4.491 H 16.601 H 14.967 31-64 L 8.195 31-64 L 7.301 MOVE OVER A LANE OR SLOW DOWN FOR EMERGENCY VEHICLES H 26.906 YEAH, IF YOU COULD NOT TEXT AND DRIVE THAT'D BE GREAT H 16.592 65+ L 10.852 65+ L 9.197 H 33.541 H 25.171 M 17 MOVE OVER AND SLOW DOWN AT CRASH SCENES ≤ 30 L 2.872 M 18 BABY YODA USES A CAR SEAT BE SAFE HE WILL ≤ 30 L 3.022 H 15.927 H 13.467 31-64 L 4.511 31-64 L 6.750 TRAVEL TIME TO I-10 8 MIN TO US-30 15 MIN H 20.656 THE RISE OF SAFE DRIVER TO END THE STREAK H 17.780 65+ L 9.581 65+ L 13.300 H 29.156 H 31.079 M = message.

Raw Human Factors Study Results C-11   Figure C-11. Average CTT scores for traffic management messages by age group and self- determined CTT difficulty level. Message A ge D iffi cu lty A ve . Sc or e Message A ge D iffi cu lty A ve . S co re I MAJOR ACCIDENT 3 MILES ≤ 30 L 1.723 SE STADIUM TRAFFIC USE BROAD ST EXIT ≤ 30 L 1.763 H 7.311 H 10.052 31-64 L 5.618 31-64 L 5.947 USE ALTERNATE ROUTES AVOID DELAYS H 13.481 THROUGH TRAFFIC USE LEFT LANE H 16.856 65+ L 10.866 65+ L 9.559 H 24.384 H 28.170 R ROADWORK 1 MILE ≤ 30 L 1.897 O ve ra ll A ve ra ge ≤ 30 L 1.794 H 13.520 H 10.294 31-64 L 6.453 31-64 L 6.006 LEFT LANE CLOSED EXPECT DELAYS H 13.177 H 14.505 65+ L 7.943 65+ L 9.456 H 19.268 H 23.941 I = incident message; R = roadwork message; SE = special event message; L = low; H = high.

C-12 Behavioral Traffic Safety Messaging on Variable Message Signs Figure C-12. Average CTT scores for BTS messages with and without humor or pop culture references by age group and self-determined CTT difficulty level. No Humor/Pop Culture Used With Humor/Pop Culture Used A ge D iffi cu lty A ve . Sc or e A ge D iffi cu lty A ve . S co re Messages with 9–11 Words ≤ 30 L 2.369 ≤ 30 L 2.607 H 7.566 H 11.884 31-64 L 3.830 31-64 L 6.075 H 11.135 H 19.484 65+ L 7.434 65+ L 9.462 H 21.373 H 25.262 Messages with 15–16 Words ≤ 30 L 2.712 ≤ 30 L 3.841 H 15.329 H 12.835 31-64 L 5.287 31-64 L 5.153 H 16.348 H 20.948 65+ L 8.764 65+ L 10.595 H 27.178 H 26.735 Messages with 18–21 Words ≤ 30 L 3.692 ≤ 30 L 3.591 H 14.004 H 12.841 31-64 L 6.195 31-64 L 6.437 H 22.758 H 18.073 65+ L 9.696 65+ L 11.694 H 29.481 H 28.370 L = low; H = high.

Abbreviations and acronyms used without de nitions in TRB publications: A4A Airlines for America AAAE American Association of Airport Executives AASHO American Association of State Highway Officials AASHTO American Association of State Highway and Transportation Officials ACI–NA Airports Council International–North America ACRP Airport Cooperative Research Program ADA Americans with Disabilities Act APTA American Public Transportation Association ASCE American Society of Civil Engineers ASME American Society of Mechanical Engineers ASTM American Society for Testing and Materials ATA American Trucking Associations CTAA Community Transportation Association of America CTBSSP Commercial Truck and Bus Safety Synthesis Program DHS Department of Homeland Security DOE Department of Energy EPA Environmental Protection Agency FAA Federal Aviation Administration FAST Fixing America’s Surface Transportation Act (2015) FHWA Federal Highway Administration FMCSA Federal Motor Carrier Safety Administration FRA Federal Railroad Administration FTA Federal Transit Administration GHSA Governors Highway Safety Association HMCRP Hazardous Materials Cooperative Research Program IEEE Institute of Electrical and Electronics Engineers ISTEA Intermodal Surface Transportation Efficiency Act of 1991 ITE Institute of Transportation Engineers MAP-21 Moving Ahead for Progress in the 21st Century Act (2012) NASA National Aeronautics and Space Administration NASAO National Association of State Aviation Officials NCFRP National Cooperative Freight Research Program NCHRP National Cooperative Highway Research Program NHTSA National Highway Traffic Safety Administration NTSB National Transportation Safety Board PHMSA Pipeline and Hazardous Materials Safety Administration RITA Research and Innovative Technology Administration SAE Society of Automotive Engineers SAFETEA-LU Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (2005) TCRP Transit Cooperative Research Program TDC Transit Development Corporation TEA-21 Transportation Equity Act for the 21st Century (1998) TRB Transportation Research Board TSA Transportation Security Administration U.S. DOT United States Department of Transportation

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Changeable, electronic, or dynamic message signs are used to provide real-time traffic information to drivers while en route to their destination. Many agencies also use these signs to display safety messages when the signs are not being used to display other traffic information. These types of messages encourage safe driving behaviors such as wearing seat belts and not drinking and driving.

The TRB Behavioral Traffic Safety Cooperative Research Program's BTSCRP Research Report 3: Behavioral Traffic Safety Messaging on Variable Message Signs provides an evidence-based approach to help guide behavioral traffic safety message design and display on variable message signs.

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