Effectiveness of Different Approaches to Disseminating Traveler Information on Travel Time Reliability (2013)

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132 The measurement of travel time reliability is an emerging prac- tice. However, a few measures appear to have technical merit and are easily understood by nontechnical audiences. Most of these measures compare days with high travel times with days with average travel times. Four recommended measures are as follows: • 90th or 95th percentile travel time; • Buffer index; • Planning time index; and • Frequency with which congestion exceeds some expected threshold (Texas A&M Transportation Institute with Cam- bridge Systematics, Inc. 2006). Frequently Used Terms The 90th or 95th percentile travel time is a time identified for a specific travel route that indicates how bad delay will be on the heaviest travel days (Texas A&M Transportation Institute with Cambridge Systematics, Inc. 2006). These travel times are reported in minutes and seconds and are thought to be easily understood by commuters familiar with their trips. For this reason, this measure is ideally suited for traveler information. This measure has the disadvantage of not being easily com- pared across trips, as most trips will have different lengths. Nor can it be easily used to combine route or trip travel times into a subarea or citywide average. Several reliability indices are presented below that enable comparisons or combinations of routes or trips with different lengths. The buffer index represents the extra time cushion (or buffer) that most travelers add to their average travel time when planning trips to account for unforeseen delays and to ensure on-time arrival (Texas A&M Transportation Institute with Cambridge Systematics, Inc. 2006). The buffer index is expressed as a percentage, and its value increases as reliability gets worse. For example, a buffer index of 40% means that for a 20-min average travel time, a traveler should budget an additional 8 min (20 min × 40% = 8 min) to ensure on-time arrival most of the time. In this example, the eight extra min- utes is called the buffer time. The buffer index is computed as the difference between the 95th percentile travel time and average travel time, divided by the average travel time. The planning time index represents the total travel time that a traveler should expect or plan on when an adequate buffer time is included (Texas A&M Transportation Institute with Cambridge Systematics, Inc. 2006). The planning time index differs from the buffer index in that it includes typical delay as well as unexpected delay. Thus, the planning time index com- pares near-worst-case travel time to a travel time in light or free- flow traffic. For example, a planning time index of 1.60 means that for a 15-min trip in light traffic, the total time that should be planned for the trip is 24 min (15 min × 1.60 = 24 min). The planning time index is useful because it can be directly com- pared with the travel time index (a measure of average con- gestion) on similar numeric scales. The planning time index is computed as the 95th percentile travel time divided by the free-flow travel time. From a data perspective, using continuous travel time data is the only way to establish reliability patterns empirically. Although predictive methods—such as the ones being devel- oped by the project team for the SHRP 2 L03 project titled Analytic Procedures for Determining the Impacts of Reliability Mitigation Strategies—may be used in a reliability monitoring system when these data are unavailable, only continuously collected travel time data can produce the actual travel time distribution from which all reliability metrics are derived. For example, the reliability metrics being used in the SHRP 2 L03 project are all derivatives of the travel time distribution. What is clear is the lack of agreement within the professional field on the terms to be used or what the mathematical calcula- tions for each of the terms should be. If the professionals cannot reach consensus on the technical terms, then the general public certainly will not do so. The purpose of the L14 project was to discover what terms the layperson would use to refer to travel C H a P T e r 1 1 Lexicon Development

133 terms that the transportation profession uses to describe the travel time reliability of a transportation system. The initial list, shown in Table 11.1, was drawn primarily from the FHWA Travel Time Reliability information brochure (Texas A&M Transportation Institute with Cambridge Systematics, Inc. 2006) and the TTI Urban Mobility Report (Schrank et al. 2011). The list also includes user interface terms identified through the review of traveler information websites conducted in prepara- tion for the surveys. The human factor studies (focus group discussions, a computer-based multiple-choice survey, an open- ended survey, the initial travel behavior laboratory study, and the enhanced laboratory study) were intended to discover what terms the layperson would use and understand to refer to travel time reliability concepts, to determine to what extent travel time reliability information would inform travel decisions, and to ascertain the value of this information to system users. Terms for some of the listed parameters were not tested in the human factor studies: (a) terms that have few or no logical alter- natives and are considered by the research team to be words or phrases that laypeople would readily recognize, (b) terms per- taining to reliability measures that would be unlikely to be used time reliability concepts and to encourage the use of those terms in communications with transportation system users. Terminology assessment The most basic considerations for trip reliability information relate to the points during a trip when reliability information should be provided, the content of the reliability information to be provided, and how content differs as a trip is made from planning and origin to ultimate destination. Another consider- ation is how reliability information needs differ for travelers with familiarity and experience making a recurrent trip com- pared with travelers making a trip without the benefit of day- to-day experience of the trip’s reliability. Likewise, how might transmission media and message content differ according to the needs of different driver types and trip purposes (e.g., older drivers or newer drivers, commercial vehicle operators or carpool organizers)? Furthermore, what innovations can assist in efficiently meeting these varying needs? The literature review, expert interviews, and technology scan completed in Phase 1 of the project identified the reliability Table 11.1. Proposed Travel Time Terms and Concepts to Be Included in Lexicon Technical Term Technical Definition 95th percentile The point on a travel time frequency distribution at which 95% of the trips made would arrive at or before the identified time Arrival time The time at which a traveler would arrive after a trip Average travel time An average of all travel times calculated over a specified time interval for a specified trip or roadway segment (The period of time over which the average is calculated is not consistent within the profession.) Buffer index A multiplier that represents the extra time or time cushion a traveler must add to his or her average travel time when planning trips to ensure on-time arrival Buffer time The average travel time multiplied by the buffer index Delay time The amount of extra time spent traveling due to congestion Departure time The time at which a traveler would depart for a trip Free-flow travel time Travel time for a trip under free-flow conditions (level of service A) Peak travel time The free-flow travel time added to the delay time Planning time The free-flow travel time multiplied by the planning time index Planning time index A multiplier that represents how much total time a traveler should allow to ensure on-time arrival Recommended departure time A time of departure calculated by a traveler information system that would ensure an on-time arrival for a given level of risk tolerance Recommended route A route between two points calculated by a traveler information system that would ensure an on-time arrival for a given level of risk tolerance Reliability Consistency or dependability in travel times, as measured from day to day or across different times of day Total trip time The total time a trip would take, door to door Travel time index Peak travel time/free-flow travel time Travel time range The range of travel times that can be expected and could be anchored by any two points on the travel time frequency distribution Trend information An indication that congestion is changing

134 trip time or worst-case scenario rather than the 95th percentile time that was intended. Arrival Time Alternate terms for arrival time—the time that a traveler arrives at his or her destination after a trip—were not tested because the phrase is commonly used. However, phrases that a traveler might use to describe a desired arrival time were presented in the computer survey. For a scenario in which a traveler would enter a preferred arrival time into a travel time calculator (to receive a recom- mended departure time), the survey offered the following phrases: • Arrive by; • Arrive at; • What time do you want to get there? • What’s the earliest you can arrive? and • What’s the latest you can arrive? By a statistically significant margin, the largest percentage of participants preferred arrive by, with arrive at the second most frequently selected option. These responses showed a willing- ness to accept either an on-time or an early arrival, since by can mean “no later than.” The other three phrases were selected much less frequently by participants. The research team con- cluded from the survey results that arrive by is the best of the tested terms to use to ask for desired arrival time input. Average Travel Time The technical definition of average travel time is an average of all travel times calculated over a specified time interval for a specified trip or roadway segment. (The period of time over which the average is calculated is not consistent within the profession.) Terms to communicate average travel time were discussed in focus groups and tested in both surveys: • Average travel time; • Estimated travel time; • Expected travel time; • Typical travel time; and • Historical travel time. Average, estimated, expected, and typical travel time were all terms that were mentioned by focus group participants. His- torical travel time is used by some travel time websites to dis- tinguish an average trip time based on past travel time data. In the open-ended survey, researchers found no clear prefer- ence for or effect on comprehension among the terms aver- age, estimated, typical, and expected travel times. However, in by laypeople (e.g., buffer and travel time indices), or (c) terms that were close parallels to other tested parameters (e.g., plan- ning time, which is similar in output to 95th percentile trip time). The following sections describe the terminology tested in the various human factor studies and results that influenced the development of the lexicon. 95th Percentile Travel Time The 95th percentile travel time is a time identified for a spe- cific travel route that indicates how long a given trip could take on the heaviest travel days (Texas A&M Transportation Insti- tute with Cambridge Systematics, Inc. 2006). The following terms for communicating 95th percentile travel times were discussed in the focus groups and/or tested in one or both of the surveys: • 95th percentile trip time; • Majority of the time; • Most of the time; • Travel time for planning; • Maximum trip time; • Worst-case trip time; and • X out of Y days (e.g., 19 out of 20 days). Of these terms, maximum trip time and worst-case trip time were not tested because of potential credibility concerns on the part of a public agency. The phrase 19 out of 20 days was not tested in surveys but is a probability expression that has been shown in the literature to be more readily understood by the general population than percentages or percentiles. Majority of the time, used as part of the sentence “The majority of the time your trip will take XX minutes or less,” was most likely to be interpreted correctly by participants as representing a trip time that would apply to unusually heavy traffic and unusual delays. This phrase was used to describe 95th percentile travel times in the enhanced laboratory study. The term 95th percentile was not well understood by survey participants, and participants who were presented with a 95th percentile trip time were less confident about arriving on time compared with participants who viewed the same trip time described with other tested terms (e.g., majority of the time, most of the time). Participants viewing 95th percentile trip time were likely to add their own buffer time on top of the total trip time provided. Most of the time, used as part of the sentence “Most of the time your trip will take __ minutes or less,” produced the greatest (expressed) confidence in arriving by the time shown; but participants still tended to add their own buffer time to the time provided. Participants given a trip time described as travel time for planning were more likely to view that time as a maximum

135 • Cushion; • Departure window; • Extra time; • Leeway; and • Recommended cushion. Of the tested terms, extra time was preferred by the most participants in the computer survey, followed by departure window; in the open-ended survey, recommended cushion, added time, and extra time all performed well. Buffer time was preferred by the fewest number of participants in the com- puter survey and so was not tested in the open-ended survey. Despite the popularity of departure window in the computer survey, the research team does not recommend its use as a synonym for buffer time. Extra time was used to describe buffer time in the travel time information provided to participants in the enhanced laboratory study. Delay Time Terminology for delay time was not tested in the human fac- tor studies; instead, terms were tested for the related concept of buffer time. Departure Time Focus group participants wanted the ability to specify a trip calculation based on time of departure or time of arrival. The computer survey continued investigation on this topic by addressing the preferred terminology to be used for the departure and arrival times. Terms and phrases tested in the survey included the following: • Departing at. • Leave at. • What time will you start your trip? • Leave by. • Departing by. • What’s the earliest you can start your trip? • What’s the latest you can start your trip? Departing at, leave at, and what time will you start your trip? were the top three terms selected by participants, show- ing a preference for specific departure times versus a range of potential departure times (as could be implied by the other four tested phrases). Free-Flow Travel Time Terminology for free-flow travel time (i.e., travel time for a trip under free-flow conditions) was not tested in the focus the computer-based survey, estimated travel time was preferred by the largest number of participants, followed by average travel time. Typical travel time and historical travel time were selected least frequently by participants in the computer-based survey. Estimated travel time was selected to describe a calculated average travel time in the enhanced laboratory study. Average travel time was addressed in two additional ways in the focus groups and in the computer survey. The sentence “It will take ___ 20 minutes to make your trip” was presented to focus groups to elicit potential terms for describing average trip time. Responses included about, an estimate of, approxi- mately, around, an average of, roughly, give or take, and at least. When tested in the computer-based survey, approximately was preferred by a majority of participants, followed by about, an estimate of, and an average of. When the sentence “It is ____ that your trip will take 45 min- utes” was completed by focus group participants and in the computer survey, estimated was preferred the highest number of participants, followed by likely and predicted. Buffer Index The buffer index represents the extra time cushion (or buffer) that most travelers add to their average travel time when planning trips to account for unforeseen delays and to ensure on-time arrival (Texas A&M Transportation Institute with Cambridge Systematics, Inc. 2006). The buffer index is expressed as a percentage, and its value increases as reliability gets worse. For example, a buffer index of 40% means that for a 20-min average travel time, a traveler should budget an additional 8 min (20 min × 40% = 8 min) to ensure on-time arrival most of the time. In this example, the eight extra minutes is called the buffer time. The buffer index is computed as the difference between the 95th percentile travel time and average travel time, divided by the average travel time. Terminology for the buffer index was not tested in the human factor studies, as this is a metric that is unlikely to be used by roadway users. Buffer Time Buffer time is defined as the average travel time multiplied by the buffer index. When speaking about the additional time added to a trip to ensure on-time arrival, focus group partici- pants suggested terms and phrases including additional time, traffic time, leeway, driving time, just-in-case time, fluff time, additional drive time, cushion, allow an additional X minutes for variables, tack on extra, and extra time. Terms that were tested in one or both surveys included the following: • Added time; • Buffer time;

136 Of the tested terms, recommended departure time was preferred most frequently by survey participants, followed by suggested departure time and estimated departure time; 95th percentile departure time was the least preferred. Recommended Route A recommended route in the context of travel time reliability is defined as the route between two points calculated by a traveler information system that would ensure an on-time arrival for a given level of risk tolerance. Terms tested in the computer survey to describe a route provided to a traveler by a traveler information system included the following: • Best route; • Forecasted trip; • Most reliable trip; • Most predictable trip; • Most consistent trip; • Historical trip conditions; and • Least variable time. Of the tested terms, the most frequently preferred was best route, followed by forecasted trip and most reliable trip. While the term recommended route was not tested in the surveys, its similarity to participant-preferred terms like recommended departure time and recommended cushion likely indicates that recommended route would also be a strong candidate. Reliability Terms for both reliability and variability were discussed in focus groups and tested in the computer survey. Most often, focus group participants chose general words such as possibly, probably, chance, or likely to describe variability at a certain time of day. Generally, they preferred that those words have a descriptor in front, such as “X% chance” or “highly likely,” to make the term less general. When talking about traffic pat- terns at a specific time of day, participants used varies, changes, and increases/decreases most often. Focus group participants preferred the terms reliable and consistent when describing the reliability of a roadway or mode. The computer survey described four different fictional trips that were actually trip times presented in different ways: a typical/average trip time, a maximum trip time, a small trip time range, and a large trip time range. Participants were then asked to select a term that they felt described each of those trip times: • Predictable; • Reliable; • Consistent; and • Best. groups or surveys. In the enhanced laboratory study, one of the graphical travel time information formats included projected trip times on a great day for travel speeds, along with corre- sponding times for average/typical and bad days. The “great day” trip time was intended to represent free-flow travel time. Peak Travel Time Terminology for peak travel time (free-flow travel time added to delay time) was not tested in the human factor studies. Terms for the similar concept of 95th percentile travel time were tested instead. Planning Time Terminology for planning time (free-flow travel time multiplied by the planning time index) was not tested in the human factor studies. Terms for the similar concept of 95th percentile travel time were tested instead; travel time for planning was one of the alternatives tested to represent 95th percentile travel time. Planning Time Index The planning time index is used to calculate the total travel time that a traveler should expect or plan on when an ade- quate buffer time is included (Texas A&M Transportation Institute with Cambridge Systematics, Inc. 2006). The plan- ning time index differs from the buffer index in that it includes typical delay as well as unexpected delay. Thus, the planning time index compares near-worst-case travel time with a travel time in light or free-flow traffic. For example, a planning time index of 1.60 means that for a 15-min trip in light traffic, the total time that should be planned for the trip is 24 min (15 min × 1.60 = 24 min). The planning time index is computed as the 95th percentile travel time divided by the free-flow travel time. Terminology for planning time index was not tested in the human factor studies, as this is a metric that is unlikely to be used by roadway users. Recommended Departure Time Recommended departure time is defined as the time of depar- ture calculated by a traveler information system that would ensure an on-time arrival for a given level of risk tolerance. The following terms were tested in the computer-based survey to describe this calculated time of departure: • Recommended departure time; • Estimated departure time; • 95th percentile departure time; and • Suggested departure time.

137 planning websites that were reviewed during focus group preparation and survey development often indicated trend information graphically (if they indicated it at all). Lexicon Format The research team identified several key elements of a lexicon entry that were deemed necessary to completely present each term. The elements are as follows: • Technical Term—the formal travel time reliability term to be defined; • Definition—a definition of the term within the reliability framework; • Usage—a general description of when an agency might use the reliability term or for what purpose it would use the term in the traveler information system; and • Recommendation—the ranking of the messages and/or terms to be used in order of preference: 44 Best—represents the term(s), phrase(s), and/or format(s) that performed the best in the human factor studies and will most likely yield the desired behavioral results when conveyed to system users; 44 Adequate—represents term(s), phrase(s), and/or format(s) that performed reasonably well in the human factor stud- ies and will not likely present significant comprehension problems for system users; and 44 Avoid—represents terms(s), phrase(s), and/or format(s) that did not perform well in the human factor studies or are recommended to avoid for noted reasons. • Alternate Phrase—an alternative term or phrases of differ- ent lengths that would work on some technology platforms but not on others; and • Information Technology Platforms—identification of appro- priate media and technology interfaces for each alternative. The list of technology platforms could continue to evolve as new media are introduced. These might include portable navigation devices, Connected Vehicle (formerly Intelli- Drive) on-board equipment, and advanced car stereo or sat- ellite radio systems. An initial list is included in Table 11.2 and includes 44 Web—intended to mean full website format viewed from a full-sized personal computer screen in a full-featured Internet browser. 44 Mobile Web—intended to mean a website format viewed from mobile devices such as smartphones and tablet computers. 44 Text—including short message service (SMS) text mes- sages and social network text messages, such as Twitter, viewed on a mobile device. 44 Mobile Application—specially designed user interfaces optimized to work on a specific smartphone operating All four terms were treated similarly by participants: they were selected to describe the typical and maximum trip times much more frequently than to describe either of the trip time ranges. Terms for trip time variability were also tested in the com- puter survey, using the sentence “Your trip time may ___ from the average trip time by 15 minutes.” Response options included the following: • Vary; • Differ; • Fluctuate; • Change; • Go up or down; • Increase or decrease; • Deviate; and • Be longer or shorter. Of these options, survey participants preferred vary most frequently, by far. Total Trip Time Terminology for total trip time was not tested in the human factor studies because the phrase is commonly used and few synonyms exist. Travel Time Savings Terminology for travel time savings was not tested in the human factor studies because the phrase is commonly used and few synonyms exist. Travel Time Range In focus groups, terms used to compete the sentence “It will take _____ 10 to 30 minutes to make your trip” were about, approximately, between, around, on average, likely, anywhere from, somewhere between, usually, and ideally. In the computer survey, two hypothetical trips for which travel time ranges were provided were not as frequently described by participants as reliable, predictable, or consistent compared with trips for which a single (typical/average or 95th percentile) trip time was provided. Historical travel time information in the first travel behavior laboratory study was presented in the form of trip time ranges. Trend Information Terms for trend information (an indication that congestion is changing) were not tested in the human factor studies. Travel

138 the related terminologies. The team developed these phrases using the general guidance for DMS message devel- opment provided in the Manual on Uniform Traffic Control Devices (MUTCD). Also note that the formatting of these travel time messages is very different from the standard messages used by state transportation agencies on DMSs. For many of the reliability terms, their use on a DMS would present various challenges to the traveler including the following: • Drivers are conditioned to see real-time travel informa- tion displayed on DMSs on freeway corridors, and reli- ability information may confuse them when placed on DMSs. • Any reliability information displayed on a DMS would need to be relative to the specific location of the sign on the freeway facility, as drivers would have begun their trips from various locations in the region’s transporta- tion network. • Messages providing departure time or buffer time infor- mation are not appropriate for DMSs because travelers would need to see the messages before starting their trip, not en route. Travel Time reliability Lexicon The following tables (Table 11.3 through Table 11.10) present the specific lexicon of phrases for each travel time reliability term tested in the various human factors studies. system. These “apps” include user input and output screens and data entry mechanisms, such as drop-down text boxes and scrolling menus, specifically designed for the touchscreen or keyboard supported by that operat- ing system. 44 Dynamic Message Sign—roadside dynamic message sign. An example format for the data elements the research team identified for travel time reliability is illustrated in Table 11.2. This structure organizes the data elements in a way that can be applied to both reliability terms at a concept level and user interface phrases and terms. This structure also provides a convenient check box matrix indicating the platforms for which each variant of the term is recommended. Limitations of Lexicon Information Note that the studies conducted in this project were labora- tory studies, and none of these terms was tested in a field environment. Only in a field test with specific detailed travel behavior data can researchers determine the true impacts and benefits of the use of travel time reliability information on behavior and resulting trip performance. Note especially that nowhere in the various human factor studies were the phrases suggested for display on DMSs tested specifically as being displayed in that format or as en route information. The phrases suggested for display on DMSs were developed by the research team on the basis of the results discussed for Table 11.2. Lexicon Format Technical Term 95th Percentile Definition The point on a travel time frequency distribution at which 95% of the trips made would arrive at or before the identified time Usage To describe the longest time a driver can expect a trip to take Recommendation Alternate Phrase Wording Context/ Additional Information Information Technology Platforms Web Mobile Web Text Mobile Applicationa Dynamic Message Sign Best 3 3 3b 3b X Adequate 3 3 3b 3b X Avoid na na na na na Note: 3 = suitable for this message; X = not recommended for this message; na = not applicable. a Mobile Web and Mobile Application did not include auditory messages. b Underlined terms to be removed from this platform (in the Wording Context/Additional Information column); other phrase shortening may be possible depending on user preference.

139 Table 11.3. Travel Time Reliability Lexicon for 95th Percentile Technical Term 95th Percentile Definition The point on a travel time frequency distribution at which 95% of the trips made would be arrive at or less than the iden- tified time Usage To describe the longest time a driver can expect a trip to take Recommendation Alternate Phrase Wording Context/Additional Information Information Technology Platforms Web Mobile Web Text Mobile Application Dynamic Message Sign Best Majority of the time “The majority of the time, your trip will take X minutes or less.” 3 3 3a 3a X MAJORITY OF TIME TRIP TO [DESTINATION] X MIN OR LESS 3 3 3 3 3b Graphical representation of the aver- age + 95th percentile 3 3 X 3 X Adequate Most of the time “Most of the time, your trip will take X minutes or less.” 3 3 3a 3a X MOST OF THE TIME TRIP TO [DESTINATION] X MIN OR LESS 3 3 3 3 3b Travel time for planning “Travel time for planning is X minutes or less.” 3 3 3a 3a X 95th percentile trip time “The 95th percentile trip time is X minutes or less.” Provide description such as “19 out of 20 days.” 3 3 3a 3a X Avoid Maximum trip time Agency concerns regarding liability and credibility na na na na na Most common trip time Worst-case trip time Note: 3 = suitable for this message; X = not recommended for this message; na = not applicable. a Underlined terms to be removed for this platform; other phrase shortening may be possible depending on user preference. b The formatting of this travel time message is very different from the standard messages used by state transportation agencies on DMSs.

140 Table 11.4. Travel Time Reliability Lexicon for Arrival Time Technical Term Arrival Time Definition The time at which a traveler would arrive after a trip Usage To tell the driver when he/she can expect to arrive at his/her destination Recommendation Alternate Phrase Wording Context/Additional Information Information Technology Platforms Web Mobile Web Text Mobile Application Dynamic Message Sign Best Arrive by “Arrive by X:XX a.m./p.m.” 3 3 3 3 X ARRIVE BY X:XX AM/PM 3 3 3 3 3a,b Adequate Arrive at “Arrive at X:XX a.m./p.m.” 3 3 3 3 X ARRIVE AT X:XX AM/PM 3 3 3 3 3a,b What time do you want to get there? This question would be used by a traveler to enter a preferred arrival time into a travel time calculator to receive a rec- ommended departure time. 3 3 X 3 X What’s the earliest you can arrive? This question would be used by a traveler to enter a preferred arrival time into a travel time calculator to receive a rec- ommended departure time. 3 3 X 3 X What’s the latest you can arrive? This question would be used by a traveler to enter a preferred arrival time into a travel time calculator to receive a rec- ommended departure time. 3 3 X 3 X Avoid na na na na na Note: 3 = suitable for this message; X = not recommended for this message; na = not applicable. a The formatting of this travel time message is very different from the standard messages used by state transportation agencies on DMSs. b Term may present ambiguity to the viewers, as they would not see a specific destination.

141 Table 11.5. Travel Time Reliability Lexicon for Average Travel Time Technical Term Average Travel Time Definition An average of historical travel times calculated over a specified time interval for a specified trip or roadway segment Usage To describe the typical travel time a driver can expect a trip will take Recommendation Alternate Phrase Wording Context/Additional Information Information Technology Platforms Web Mobile Web Text Mobile Application Dynamic Message Sign Best Estimated travel time “Estimated travel time is X minutes.” 3 3 3a 3a X “It is estimated that your trip will take X minutes.” 3 3 3a 3a X EST THAT TRIP TO [DESTINATION] WILL TAKE X MIN 3 3 3 3 3b Approximate travel time “It will take approximately X minutes to make your trip.” 3 3 3a 3a X APPROX X MIN TO [DESTINATION] 3 3 3 3 3b Adequate Typical travel time “Typical travel time is X minutes.” 3 3 3a 3a X Graphical representation of the average + 95th percentile (typical day and bad day) 3 3 X 3 X Graphical representation of the 20th percentile + average + 95th percentile (good, typical, and bad day) 3 3 X 3 X Average travel time “Average travel time is X minutes.” 3 3 3a 3a X Expected travel time “Expected travel time is X minutes.” 3 3 3a 3a X Avoid Historical travel time Difficult to determine relevance with no comparison to real-time information na na na na na Note: 3 = suitable for this message; X = not recommended for this message; na = not applicable. a Underlined terms to be removed for this platform; other phrase shortening may be possible depending on user preference. b The formatting of this travel time message is very different from the standard messages used by state transportation agencies on DMSs.

142 Table 11.6. Travel Time Reliability Lexicon for Buffer Time Technical Term Buffer Time Definition The average travel time multiplied by the buffer index Usage To describe how much extra time a driver should plan for a trip he/she wishes to take Recommendation Alternate Phrase Wording Context/Additional Information Information Technology Platforms Web Mobile Web Text Mobile Application Dynamic Message Sign Best Extra time “Extra time for trip is X minutes.” 3 3 3a 3a X EXTRA TIME TO [DESTINATION] IS X MIN 3 3 3 3 X Adequate Added time “Added time for trip is X minutes.” 3 3 3a 3a X ADDED TIME TO [DESTINATION] IS X MIN 3 3 3 3 X Recommended cushion “Recommended cushion for trip is X minutes.” 3 3 3a 3a 3 Avoid Cushion Preference shown for other terms na na na na na Buffer time Departure window Leeway Note: 3 = suitable for this message; X = not recommended for this message; na = not applicable. a Underlined terms to be removed for this platform; other phrase shortening may be possible depending on user preference. Table 11.7. Travel Time Reliability Lexicon for Departure Time Technical Term Departure Time Definition The time at which a traveler would depart for a trip Usage To indicate the time a traveler departs for a trip. For DMS applications, message would need to be set in context with other information, such as destination, travel time, or route. Recommendation Alternate Phrase Wording Context/Additional Information Information Technology Platforms Web Mobile Web Text Mobile Application Dynamic Message Sign Best Departing at “Departing at X:XX a.m./p.m.” 3 3 3 3 X Leave at “Leave at X:XX a.m./p.m.” 3 3 3 3 X Adequate What time will you start your trip? This question would be used by a traveler to enter a start time into a travel time calculator to receive an arrival time. 3 3 X 3 X Leave by “Leave by X:XX a.m./p.m.” 3 3 3 3 X Departing by “Departing by X:XX a.m./p.m.” 3 3 3 3 X What’s the earliest you can start your trip? This question would be used by a traveler to enter a start time into a travel time calculator to receive an arrival time. 3 3 X 3 X What’s the latest you can start your trip? This question would be used by a traveler to enter a start time into a travel time calculator to receive an arrival time. 3 3 X 3 X Avoid na na na na na Note: 3 = suitable for this message; X = not recommended for this message; na = not applicable.

143 Table 11.8. Travel Time Reliability Lexicon for Recommended Departure Time Technical Term Recommended Departure Time Definition A time of departure calculated by a traveler information system that would ensure an on-time arrival for a given level of risk tolerance. Usage To indicate the time a driver should depart for a trip to ensure he/she arrives at his/her destination on time. For DMS applications, message would need to be set in context with other information, such as destination, travel time, or route. Recommendation Alternate Phrase Wording Context/Additional Information Information Technology Platforms Web Mobile Web Text Mobile Application Dynamic Message Sign Best Recommended departure time “Recommended departure time is X:XX a.m./p.m.” 3 3 3a 3a X Adequate Suggested departure time “Suggested departure time is X:XX a.m./p.m.” 3 3 3a 3a X Estimated departure time “Estimated departure time is X:XX a.m./p.m.”b 3 3 3a 3a X 95th percentile departure time “The 95th percentile departure time is X:XX a.m./p.m.” Provide description such as “19 out of 20 days.” 3 3 3a 3a X Avoid na na na na na Note: 3 = suitable for this message; X = not recommended for this message; na = not applicable. a Underlined terms to be removed for this platform; other phrase shortening may be possible depending on user preference. b Can be used if term is NOT being used to mean average trip time.

144 Table 11.9. Travel Time Reliability Lexicon for Recommended Route Technical Term Recommended Route Definition A route between two points calculated by a traveler information system that would ensure an on-time arrival for a given level of risk tolerance Usage To describe the route a driver should take for a planned trip to ensure he/she arrives on time to his/her destination Recommendation Alternate Phrase Wording Context/Additional Information Information Technology Platforms Web Mobile Web Text Mobile Application Dynamic Message Sign Best Best route “Best route is via [facility].” 3 3 3a 3a X BEST ROUTE TO [DESTINATION] TAKE [FACILITY] 3 3 3 3 3b Adequate Forecasted trip “Forecasted trip is via [facility].” 3 3 3a 3a X FORECASTED TRIP TIME VIA [FACILITY] X MIN 3 3 3 3 3b Most reliable trip “Most reliable trip is via [facility].” 3 3 3a 3a X MOST RELIABLE TRAVEL TIME TO [DESTINATION] TAKE [FACILITY] 3 3 3 3 3b Most predictable trip “Most predictable trip is via [facility].” 3 3 3a 3a X MOST PREDICTABLE TRAVEL TIME TO [DESTINATION] TAKE [FACILITY] 3 3 3 3 3b Most consistent trip “Most consistent trip is via [facility].” 3 3 3a 3a X MOST CONSISTENT TRAVEL TIME TO [DESTINATION] TAKE [FACILITY] 3 3 3 3 3b Avoid Historical trip conditions Difficult to determine relevance with no comparison to real-time information; preference shown for other terms na na na na na Least variable time Note: 3 = suitable for this message; X = not recommended for this message; na = not applicable. a Underlined terms to be removed for this platform; other phrase shortening may be possible depending on user preference. b The formatting of this travel time message is very different from the standard messages used by state transportation agencies on DMSs.

145 Table 11.10. Travel Time Reliability Lexicon for Reliability Technical Term Reliability Definition Consistency or dependability in travel times between two points, as measured from day to day or across different times of day Usage To describe the variability of travel times to drivers so they can plan their trip with more robust information Recommendation Alternate Phrase Wording Context/Additional Information Information Technology Platforms Web Mobile Web Text Mobile Application Dynamic Message Sign Best Predictable “Most predictable trip” 3 3 3 3 X Adequate Reliable “Most reliable trip” 3 3 3 3 X Consistent “Most consistent trip” 3 3 3 3 X Vary “Trip varies.” 3 3 3 3 X Avoid Differ Preference shown for other terms na na na na na Fluctuate Change Go up or down Increase or decrease Deviate Note: 3 = suitable for this message; X = not recommended for this message; na = not applicable.