Changeable Message Sign Displays During Non-Incident, Non-Roadwork Periods (2008) / Chapter Skim
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15 STATUS OF CHANGEABLE MESSAGE SIGNS Background Once a CMS system is installed, a question always arises concerning when messages should be displayed during non-incident/non-roadwork periods. There are the following two schools of thought on this topic: 1.
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CMSs sitting idle for several months prompted New York DOT to adopt a policy of displaying some type of message on the freeway CMSs at all times. Survey Results General A summary of the status of the CMSs during non-incident/ non-roadwork periods reported by the agencies that responded to the questionnaire is shown in Figure 2.
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17 • Test the CMSs, so the public knows they are working. Do not test the signs with a time and temperature display feature (1 TMC)
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Messages Displayed Public Response to Messages Displayed during Non-Incident/ Non-Roadwork Periods Twenty-three of the 45 TMCs (51%) that regularly or periodically display messages during non-incident/non-roadwork periods as an alternative to leaving the signs blank reported a very favorable (22%)
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19 messages during the peak, off-peak, or both, when incidents or roadwork are not present are summarized in Figure 7. Ninety-three percent stated that they do not have plans to change their policy, whereas 7% plan to change.
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• Display of historic travel times; and • Daily repetition of the same travel times displayed to commuters. First, as previously noted, current technology does not allow TMCs to accurately predict travel times; therefore, recent historical travel times are displayed.
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21 Agency/Traffic Management Center Location Peak Off-Peak California Department of Transportation • Irvine • Los Angeles • Oakland • Sacramento • San Bernardino • San Diego X X X X X X X X X X X X X X X X X Colorado DOT • Golden (statewide) X Delaware Department of Transportation (statewide)
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Reasons for Not Displaying Travel Time The primary reasons cited as to why travel-time information was not displayed were that (1) infrastructure and/or software was not available and (2)
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23 • Drivers were slowing down to read the signs (2 TMCs)
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• It is not necessary to display travel times on all CMSs. Some CMS locations do not lend themselves to traveltime messages (1 TMC)
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25 that travel time was not displayed owing to the lack of funding to implement the necessary hardware and software. CONGESTION MESSAGES Background Sometimes CMSs are used to present information about traffic conditions when the freeway becomes congested.
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During the off-peak, 69% of the TMCs reported that congestion messages are not displayed during non-incident/ non-roadwork periods. Thirty-one percent stated that congestion messages are regularly or periodically displayed.
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27 Examples of Typical Congestion Messages Exhibit 4 shows examples of typical messages that were reported by the 35 of 100 TMCs that regularly or periodically display congestion messages rather than leaving CMSs blank. Experiences and Lessons Learned The experiences and lessons learned most noted by the TMCs that display congestion messages was that the messages must be accurate and up to date.
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ogy and issues created by congestion in this area. Providing congestion information to motorists allows the local commuter to consider an alternate route or arterial and provides additional information to unfamiliar motorists so that they may drive more safely on roadways with which they are not familiar (1 TMC)
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29 resulted in a lower percentage of subjects who indicated they would divert than did the message HEAVY CONGESTION. Several studies have been conducted to evaluate advisory speed messages on CMSs in highway work zones.
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Concerns and Challenges Only three comments were received regarding concerns and challenges. Specific comments follow: • A concern and challenge is maintaining credibility.
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31 Public Response The reported public response is summarized in Figure 26. Only 17% of the TMCs that display PSAs as an alternative to leaving the CMSs blank reported that they received a favorable response from the public.
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32 • A message should be run for a short period of time and/or should not be displayed too often (8 TMCs)
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33 non-traffic-related messages if PSAs are posted. Some TMCs voiced differences of opinion with agency administration/ management about displaying PSAs.
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administrative/upper-management preference, TMC manager/ supervisor preference, both administrative and TMC preference, or as part of governor safety program, statewide safety program, or law enforcement agency request. Only 1% of the TMCs included research results in their decision.
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35 • Post only during off-peak or in off-peak direction to minimize unintended congestion (2 TMCs)
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• Trying to avoid private-interest type requests (1 TMC)
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37 display traffic law or ordinance messages rather than leaving CMSs blank. Experiences and Lessons Learned Only a few TMCs reported on their experiences and lessons learned with displaying traffic law or ordinance messages.
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• Received positive feedback from law enforcement when conducting routine traffic stops in areas where messages are displayed. For example, we have a message explaining the Texas law requiring traffic to move over when an emergency vehicle is stopped on the roadway.
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