Effectiveness of Disseminating Traveler Information on Travel Time Reliability: Implement Plan and Survey Results Report
CHAPTER 11. FINAL REMARKS
As stated previously, the report A Lexicon for Conveying Travel Time Reliability Information, developed as part of the Strategic Highway Research Program 2 (SHRP2) Reliability Project L14 – Effectiveness of Different Approaches to Disseminating Traveler Information on Travel Time Reliability – established a preliminary set of suggested terminology and guidelines for conveying Travel Time Reliability (TTR) information to road users so that they may make optimal travel choices from their point of view, such as whether to take a trip or not, departure time, mode choice, and route choice. Specifically, a Lexicon of phrases was developed for each of eight TTR terms. Each Lexicon contained detailed guidelines for TTR information that would most likely be understood and used by the travelers.
The documented limitation of the initial research was that the Lexicon terminology and guidelines were developed as part of laboratory studies, and none of the terms were tested in a field environment. The intent of this project was to begin to assess the real-world impacts of using this information so that operating agencies could better deploy and use the recommended Lexicon terminology. The results of that research are presented herein, and the salient findings are provided below.
The field study permitted statistical comparison of the Lexicon terminology across three different information channels and for two different Lexicon assemblies. The study spanned different physical locations and utilized participants with different demographic and travel characteristics. Statistical models adjusted for these exogenous factors, which did prove to be important to properly interpreting the results of interest for the Lexicon assemblies and information channels. The city of the participants only rarely appeared as a significant factor in the models, suggesting that location was not an important differentiator in the outcomes. Among other exogenous variables, though, education level and the number of Phase 2 trips taken with the TTR information were found to significantly correlate with responses for multiple questions. Specifically, those participants with college degrees and those taking more trips in the TTR phase were less likely to report that they had made changes to either a familiar or unfamiliar trip as a result of the information. This finding was reinforced by the fact that in subsequent survey questions, these two groups were identified as finding TTR information less useful and reliable, and disagreeing that it reduced their travel time or their travel stress.
Lexicon Assemblies/Alternate Wording
Observation: Only one survey question of seventeen evaluated resulted in statistically significant differences between the Lexicon assemblies. Those that were provided Assembly A were more likely to change their trip plans for a familiar trip than those provided Assembly B. It should be noted that across all the questions evaluated, no multiple comparison adjustments were made to the statistical test results. Therefore, any "statistically significant" result has a potential to have been reached in error. Across a large number of such results, it becomes likely that a significant result really represents only random variability in the responses and should be evaluated with caution.
Recommendation: Given that the statistical analysis of the study data showed that Assembly A was found to significantly increase the likelihood of behavior change on familiar trips due to TTR information compared with Assembly B (shown previously in Figure 30), the study team recommends that the initial Lexicon tables developed as part of SHRP2 L14 be modified to reflect the noted preference for Assembly A over B for familiar trips. Only nominal changes need to be made, because in all but one case those terms noted as "best" remained so. In the case of "Average Travel Time," one of the "best" terms performed better than the other, so the other term can be moved to "adequate." As a result, the "Average Travel Time" table was modified in the companion document to demote "Approximate travel time" from "Best" to "Adequate".
Information Channel for Delivering Travel Time Reliability Information
Observation: Throughout the survey responses, there were several instances showing lower utility or satisfaction for the 511 information channel than either of the Web or App access channels. In a few instances, the App access demonstrated superior responses to both 511 and the Web. The preference of dissemination platform in terms of appeal to users is (1) application, (2) website, and (3) 511 system.
Recommendation: Given the lower preference for the 511 system, it is not recommended that an agency develop a 511 system solely for the purpose of providing TTR information. Rather, if an agency develops a system for its existing applications (e.g., mobile application, mobile website, traditional website) and already has a 511 system, the agency may also want to provide the TTR information via 511 since the mechanism to transfer that information to a 511 system is fairly straightforward.
Value of Travel Time Reliability Information
As discussed in the original SHRP2 research, the expectations were that TTR information might have value to travelers in specific circumstances and for specific types of trips rather than for every type of trip on a daily basis. Typical circumstances where travelers might perceive a benefit would be for drivers new to a region trying to plan trips in the unfamiliar landscape, or familiar drivers taking unfamiliar trips on either new routes or to new destinations at unfamiliar times of the day. Furthermore, the original research discussed the fact that drivers may underestimate the realized benefit of TTR information in terms of reduced delay, improved on-time reliability, and reduced stress. Additionally, the value of the TTR information for travelers – especially those unfamiliar to a region – would decline over time as they gain familiarity with the region and the overall aspects of congestion and performance of the regional network.
Observation: It is important to note that the results of this study provided mixed and/or inconclusive results in terms of the value and benefit of TTR information to travelers. Those survey participants who reported using TTR information used it for unfamiliar trips less frequently than they did for familiar trips. The reasons for this difference were not obvious from the survey responses. On the other hand, the most common reason for not using TTR information expressed by those survey participants who never used it was that they did not need it for familiar trips. This finding indicates that these participants did not believe that the information would be helpful to them for their regular commutes or likely any other trips, so they did not use it. It also indicates that they may not fully understand how the information could have helped them for these trips by providing a snapshot of typical conditions for specific time periods. Educating potential users might help improve this understanding and, therefore, increase its use in future applications.
For the field study, the inconclusiveness of the value of TTR information could be attributed to a variety of factors. First, travelers may have primarily accessed the information for recurrent trips to familiar locations, thereby possibly offering only nominal value to the user. This trend would support the original hypothesis that drivers would find the information more useful for unfamiliar trips. Second, the lack of TTR information on alternate routes in two of the three locations may have limited the opportunity or willingness of users to change to less familiar routes in those locations. Thus, they may have felt that the provided TTR information did not have much value. Third, when completing the final user survey, drivers may have underestimated the benefits of the TTR information on their on-time performance, again supporting the finding from the original research as noted above.
Recommendation: While the overall results were somewhat inconclusive in terms of the value of TTR, they tend to support the findings of the original research indicating that the overall intrinsic value of TTR information alone is better for specific trips rather than for all types of trips. Combining this information with real-time information may further enhance the value to travelers by providing context for the current conditions on facilities. Additionally, providing an easy-to-understand explanation of the TTR information might help improve usage of the information.
