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Suggested Citation:"Chapter One - Introduction." National Academies of Sciences, Engineering, and Medicine. 2008. Changeable Message Sign Displays During Non-Incident, Non-Roadwork Periods. Washington, DC: The National Academies Press. doi: 10.17226/23070.
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Suggested Citation:"Chapter One - Introduction." National Academies of Sciences, Engineering, and Medicine. 2008. Changeable Message Sign Displays During Non-Incident, Non-Roadwork Periods. Washington, DC: The National Academies Press. doi: 10.17226/23070.
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Suggested Citation:"Chapter One - Introduction." National Academies of Sciences, Engineering, and Medicine. 2008. Changeable Message Sign Displays During Non-Incident, Non-Roadwork Periods. Washington, DC: The National Academies Press. doi: 10.17226/23070.
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5GENERAL PURPOSE OF CHANGEABLE MESSAGE SIGNS Road signs exist to communicate information to motorists. Static guide signs are permanent and are limited to presenting information that is largely “geographically linked.” Change- able message signs (CMSs) can present up-to-the-moment traffic and roadway information. CMSs are programmable traffic control devices that can usually display any combination of characters to present messages to motorists. These signs are either permanently in- stalled above or on the side of the roadway or portable de- vices attached to a trailer or mounted directly on a truck and driven to a desired location. Portable CMSs are much smaller than permanent CMSs and are oftentimes used in highway work zones, when major crashes or natural disasters occur, or for special events (e.g., sporting events). This synthesis addresses only permanent CMSs. When installed, CMSs become a part of the total motorist information system. Thus, the information presented on CMSs and the placement of the signs must be consistent and compatible with static signs used on the freeway. CMSs perform a critical role on freeways. Such signs can furnish motorists with real-time traveler information that can advise them of a problem and, in some cases, a suggested course of action. CMSs also are used to improve motorist safety and reduce traffic congestion and delay. Additionally, CMSs can be used to manage traffic by displaying early warn- ing, advisory, and alternative route messages. BACKGROUND It has been estimated that more than $300 million has been spent in the deployment of CMSs in the United States. CMSs as defined in the Manual on Uniform Traffic Control Devices (MUTCD) are sometimes referred to as dynamic message signs (DMSs) or variable message signs (VMSs) (1). Perma- nently mounted CMSs are used primarily for the following applications: • Non-recurrent problems—caused by random, unpre- dictable incidents such as crashes; stalled vehicles spilled loads; or caused by temporary, preplanned activities such as construction, maintenance, or utility operations. • Environmental problems—caused by acts of nature such as fog, floods, ice, snow, etc. • Special event traffic problems—problems associated with special events (e.g., ball games and parades). • Special operational problems—operational features such as high occupancy, reversible, exclusive, or contraflow lanes; and certain design features such as drawbridges, tunnels, and ferry services. • AMBER (America’s Missing: Broadcast Emergency Response) alerts—notification program to help locate missing children believed to have been abducted. When the CMSs are not used for the aforementioned applications, the traditional wisdom has been to leave per- manent CMSs blank. However, some state departments of transportation (DOTs) are using their CMSs to display other types of messages during non-incident/non-roadwork periods. Provisions in the MUTCD allow agencies to display safety- campaign messages and non-incident, transportation-related messages (1, §2A.07). Certain types of messages, such as travel-time information and AMBER alerts, are gaining popularity among state DOTs. These practices may lead to more frequent use of CMSs. However, there is concern that more frequent use of these non-incident/non-roadwork transportation-related messages can compromise the cred- ibility of the CMSs. If CMSs distract drivers from more critical tasks while traveling at prevailing speeds, or if the messages are erroneous or outdated, then driver acceptance can be compromised. In addition, if the messages are too long, complex, and/or confusing to read and comprehend, drivers may reduce speed to read the messages and this could result in a potential safety problem. Guidelines for the design and display of CMS messages for incidents and roadwork are available. However, guidelines are not available for messages displayed during non-incident/ non-roadwork periods, and information is not available con- cerning state practice regarding messages displayed during non-incident/non-roadwork periods. SYNTHESIS OBJECTIVES The objective of this synthesis was to provide current informa- tion concerning the display of messages during non-incident/ non-roadwork periods gathered from the literature and state, toll road, turnpike, and parkway transportation agencies that operate permanent CMSs. (In subsequent sections of this CHAPTER ONE INTRODUCTION

synthesis, permanent CMSs are referred to as CMSs.) Infor- mation gathered for this synthesis included the following: • Agency policies, guidelines, practices, and procedures for displaying or prohibiting messages during non-incident/ non-roadwork periods in both urban and rural areas; • Categories of messages displayed; • Prioritization of messages displayed and rank order, if applicable; • Message content; • Experiences and lessons learned by agencies about dis- playing messages [e.g., travel time, AMBER alert, public service announcements (PSAs), and other non-incident, non-roadwork messages] or leaving CMSs blank, in- cluding information gained from public reaction or feed- back, surveys, and focus groups; and • Results from completed and on-going research concern- ing the design, display, and operation of CMSs, espe- cially as related to human factors issues. The primary intent of this synthesis was to identify prac- tices that have proven effective, as well as those that have not. 6 It serves as a guide to states and other transportation agencies in making more effective use of CMSs for non-incident/ non-roadwork messages. STUDY APPROACH A review of the literature was conducted to evaluate relevant results from completed and on-going research concerning the design, display, and operation of CMSs related to human fac- tors issues. In addition, an online survey was conducted to obtain current practice from state DOTs and toll road agen- cies that operate CMSs. The questionnaire developed for the survey was sent to 50 state DOTs and 10 toll road agencies that operate CMSs. An e-mail with the online questionnaire was sent in mid- February 2007 to members of the AASHTO Subcommittee on Operations and Management and to the 10 toll road agen- cies. Because it was likely that the practice of displaying CMS messages during non-incident/non-roadwork periods varied among the traffic management centers (TMCs), instructions 1 AMBER alert 21 Rain 2 Roadwork 22 Homeland security 3 Incidents 23 Truck restrictions 4 Flood 24 Sand/dust 5 Advance notice of upcoming roadwork 25 Advance notice of holiday/recreation traffic 6 Ice on road 26 HOV lanes 7 Snow on road 27 Hazardous cargo 8 Planned special events 28 Mountain pass control 9 Special high-volume traffic (e.g., holiday weekend) 29 Bridge control 10 Evacuation during chemical spills 30 Tunnel control 11 Fog 31 Contra-flow lanes 12 Snow 32 Reversible lanes 13 High water but passable 33 Inter-modal (e.g., ferry schedule, Amtrak) 14 Evacuation during terrorist attack 34 Mixed-flow managed lanes 15 Evacuation during wildfire 35 Advanced parking system 16 Wind 36 International border crossing 17 Support of highway advisory radio 37 Exclusive lanes 18 Advance notice of special event 38 Highway/railway grade-crossing 19 Evacuation during hurricane 39 Highway/light rail transit crossing 20 Smog/ozone 10099 98 85 84 83 77 73 67 65 64 63 62 60 56 55 52 49 48 43 41 40 39 30 23 22 21 18 17 16 14 14 14 8 7 4 4 1 0 0 10 20 30 40 50 60 70 80 90 100 1 3 5 6 72 4 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 Message Type Pe rc en t o f T M Cs FIGURE 1 Current applications of CMSs.

7in the e-mail requested that the questionnaire be forwarded to the manager/supervisor of all TMCs within the agency. The questionnaire, as shown in Appendix A, contained several decision logic branches so that certain questions were automatically skipped based on responses to other questions. Therefore, a respondent completing the questionnaire online may not have seen all of the questions that are shown in the version in Appendix A. In addition, some of the questions in the online version were shown in a slightly different format. The questionnaire was structured to highlight the follow- ing types of non-incident/non-roadwork messages, which, based on the experience of the author and a review of the lit- erature, would most likely be the types of messages that may be regularly or periodically displayed by the transportation agencies as an alternative to leaving CMSs blank: • Travel time, • Congestion, • Speed, • Safety campaigns, • PSAs, and • Traffic law or ordinances. Although AMBER alert messages are displayed for child abductions and not as a substitute for leaving the CMSs blank, the survey provided an opportunity to obtain more informa- tion on issues relative to displaying AMBER alert messages. The survey was also used to determine the other types of messages that the transportation agencies currently display. Therefore, after self-identification questions, the respondents were presented with a list of 39 message applications related to traffic operations and were asked to identify the types of messages that they currently display on CMSs. The list of message applications included incidents, roadwork, and other types of messages that would be used for specific applica- tions (e.g., non-recurrent, environmental, special event traf- fic, and special operations problems). The list did not include travel time, congestion, speed, PSAs, safety campaign, or traf- fic law and ordinance messages because they were addressed separately in the questionnaire. However, AMBER alert was one of the message types included in the list. AGENCY RESPONSE TO SURVEY Responses were received from 40 state DOTs and 6 toll road agencies with a total of 100 TMCs. The TMCs operated 3,023 CMSs in urban areas and 821 CMSs in rural areas. Forty-two TMCs operated CMSs only in urban areas, 8 only in rural areas, and 50 in both urban and rural areas. A list of the agencies and the TMCs within each agency that com- pleted the questionnaire and the number of CMSs operated by each is shown in Appendix B. CURRENT APPLICATIONS OF CHANGEABLE MESSAGE SIGNS As a starting point to the objectives of the survey conducted as part of the study, the TMCs were asked to identify current applications of CMSs. The results are shown in Figure 1. Of particular interest is that all of the TMCs that responded to the questionnaire display AMBER alert messages. In addi- tion, 99% display roadwork messages and 98% display inci- dent information. The lone exception to roadwork messages was one toll road agency. The exception to incident informa- tion was one state DOT that has two TMCs that operate a small number of CMSs only in rural areas.

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TRB’s National Cooperative Highway Research Program (NCHRP) Synthesis 383: Changeable Message Sign (CMS) Displays During Non-Incident, Non-Roadwork Periods explores the use of CMSs to convey messages on non-recurrent, environmental, special event traffic, and other special problems.

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