Road Management Journal
Copyright © 1997 by TranSafety, Inc.
November 1, 1997
Fax: (360) 335-6402
Variable-message signs (VMSs) on U.S. roadways provide a variety of informational messages about traffic conditions. A case study of the VMS system of Northern Virginia assessed motorist attitudes toward VMSs and the effect of demographic characteristics on those attitudes. Study results revealed that demographics were essentially negligible in relation to VMSs and, overall, motorists "are well disposed toward new types of VMS messages that are simple, reliable, and useful." Brien G. Benson detailed the results of the study in "Motorist Attitudes About Content of Variable-Message Signs" (Transportation Research Record 1550).
The study involved seven focus groups and an opinion survey. The focus groups comprised 125 participants from various places of employment in the study area. These groups were used to help formulate questions for the survey, to supplement the survey findings, to clarify and offer insights about motorist attitudes that the survey could not determine, and to assess attitudes that researchers could not examine in the survey because of time constraints.
The survey consisted of 517 computer-assisted telephone interviews. Interviewers asked respondents their age, education, income, gender, and how often they used freeways. The study as a whole focused on motorist attitudes regarding the content of VMSs. As such, "it complement[ed] other VMS research in the United States, which has tended to focus on human factors and on VMSs as part of integrated traffic control systems."
Survey responses made up the bulk of the study findings; results from focus groups supplemented and complemented those responses. With a few exceptions, "no significant correlation between motorist attitudes and demographic variables was found." One such exception was a small negative correlation between education level and support for VMS safety messages. The authors speculated that well-educated motorists "are more likely to resent being lectured about safety, or at least to consider safety reminders as unnecessary."
In response to a question regarding how often VMSs influenced their driving, half the survey respondents (254) replied "often," two-fifths (195) said "occasionally," and the remainder (67) stated "not at all." In other words, half the respondents depended regularly on VMSs, which was consistent with attitudes expressed in the focus groups.
Only one-third of the respondents said they had witnessed inaccurate or out-of-date information on VMSs. The researchers considered this "puzzling," since occasional inaccurate information on VMSs is a given. Based on that fact, a number of participants in the focus groups advised more regular traffic information updates. For example, posting the time when a traffic report was first displayed on a VMS would help drivers weigh its relative accuracy. Most respondents (140 of 160) favored this technique. Fewer (60 of 160) liked the idea of a 900 phone-in number that would allow drivers to report inaccurate VMS information. A lack of cellular phones and an inherent distrust of the efficacy of such an approach may have accounted for the lukewarm response.
In the face of heavy congestion, three-fifths of the respondents said they would be "very likely" to try an alternative route posted on a VMS, and another third stated they would be "somewhat likely" to do this. Focus group participants "overwhelmingly" cited "fear of getting lost" as their most common reason for not trying an alternate route suggested by a VMS. Survey respondents listed "getting lost" as only one of four reasons for not taking an alternate route, possibly because they felt getting lost "was a less socially acceptable answer." But there was nearly complete support (97 percent) for posting the exact location of an accident, and "very strong support" (75 percent) for posting an anti-rubbernecking message such as "Accident Ahead/All Lanes Open/Maintain Speed."
Responses varied concerning the posting of delays in travel time based on heavy congestion, but essentially half the respondents wanted that information to be quantitative and half favored a descriptive approach. Many participants in the focus groups were skeptical about the value of this information in any form, since posting delays would do nothing to alleviate the problem of heavy congestion. Many also felt such estimates would be inaccurate more often than not, which would only compound an already-frustrating situation.
Two-thirds of survey respondents supported posting safety messages on VMSs; they found specific messages such as "lights on in bad weather" preferable to general messages such as "tailgating is deadly." This was in contrast to the focus groups, where most participants thought VMSs should post only traffic and roadway conditions. Two-fifths of survey respondents also indicated they would be willing to pay for traffic information, specifically for 900 telephone calls (presumably made from car cellular phones) that would offer current, route-specific information. One-third said they would pay for a pager service to warn motorists of significant, route-specific changes in traffic conditions.
Respondents reacted to several possible ways of posting information on VMSs. Motorists were not enthusiastic about using VMSs to display television pictures of roadway conditions, whereas reactions were half for and half against using VMSs to display maps that illustrated traffic conditions. Almost all (90 percent) strongly encouraged locating VMSs on streets feeding onto freeways.
Participants in focus groups also made suggestions about issues not included in the survey. Many felt displaying obvious traffic information (such as "Congestion Ahead" during rush-hour traffic) was a distraction rather than a help. Opinions varied on both the advisability of displaying traffic conditions occurring 15 or more miles ahead and the need for posting causes of congestion delays. Several focus group participants thought VMSs were poorly located, and many thought VMSs should refer drivers to highway-advisory radio, which can handle significantly more traffic information than can be displayed on VMSs.
A major finding of the study was that "demographic variables appear to have very little influence on motorist attitudes toward VMSs." As a result, "efforts to target VMSs to one or another group would be misplaced and . . . VMS message content may be managed without undue concern for equity or other distributional effects." Roughly half the drivers routinely relied on VMSs and half did not, but respondents in general favored VMS messages defined by simplicity, reliability, and usefulness. A message providing the precise location of an accident would meet these three criteria, while presumably delay time estimates and safety messages would not.
Copyright © 1997 by TranSafety, Inc.