Principles and Guidance for Presenting Active Traffic Management Information to Drivers (2021)

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42 Chapter 4: Research Gaps Overview Based on the findings from the State of Practice and Literature Reviews, we conducted an analysis to refine and prioritize research gaps. To complete the gap analysis, we used a structured approach utilized in previous gap analyses (e.g., Richard et al., 2012; Richard et al., 2013). Based on the results of previous activities, we identified 13 research gaps focusing on how the evolving alternative information channels will impact the role of DOT infrastructure and messaging practices. While each of these research gaps relates to one of more of the 6 key research questions that are the focus of this project, they contain additional detail and context about the underlying issues and provide additional focus to the key research questions. See Appendix C for full descriptions of the research gaps and Table 11 for connections between the 6 key research questions and 13 research gaps. Research Gap Descriptions 1. DMS with a message about “low visibility” or “slow traffic ahead” can alert drivers to the need to reduce speeds, while dynamic speed limit signs can reduce the variability of the reduced speeds by providing a specific number. Dynamic speed limits are sometimes deployed as a standalone system or do not contain a message about why there is a reduced speed in place, and lack of driver understanding about the meaning of the signage can further hinder effectiveness. Does the provision of additional information as an explanation to justify and encourage travel at reduced speeds increase the effectiveness of a dynamic speed limit with better speed compliance and lower average speed, e.g., “low visibility” or “congestion ahead” via supplemental DMS or dynamic elements on the dynamic speed limit signs? (Q1 or Q216) 2. Locations differ in the provision of static signage in advance of an ATM deployment with lane control signage, one example is shown in the photo below. This may be done for legal reasons for enforcement purposes; as a condition in the legislation allowing the deployment of a new strategy such as dynamic speed limits or a dynamic shoulder lane that is a change from current practices; or simply for informational purposes to help drivers understand. Is there a benefit of increased driver understanding in providing static signage in advance of ATM deployments to explain symbols? (Q1) 3. Dynamic information can be disseminated to drivers using various media, whether agencies provide information for drivers via infrastructure, to vehicles for in-vehicle messaging, to third-party providers for smartphone applications, or a combination of these approaches. What media is the best for disseminating dynamic information to satisfy driver wants and needs? Examination of this question in the context of dynamic queue warning may provide insightful results, as this dynamic information can be given to drivers without the presence roadside infrastructure. (Q1, Q3) 16 These notations (Q1, Q2, etc.) refer to which of the 6 original research questions the individual research gap is associated with.

43 4. Dynamic information can be disseminated to drivers using various media, whether agencies provide information for drivers via infrastructure, to vehicles for in-vehicle messaging, to third-party providers for smartphone applications, or a combination of these approaches. What media for disseminating dynamic information achieves the lowest driver distraction, highest driver understanding and usage, and largest safety and mobility benefits? Examination of this question in the context of dynamic queue warning may provide insightful results, as this dynamic information can be given to drivers without the presence roadside infrastructure. (Q2, Q3, Q4) 5. As an alternative to deploying and maintaining a sign over each lane, a single dynamic message sign might present similar dynamic lane control information in the form of a pictogram. Are lane closure pictograms on a DMS understood by drivers, and is it equally or more effective than information presented via overhead dynamic lane control signs? (Q4) 6. In order to reduce the costs of deploying and maintaining ATM infrastructure, some agencies are considering alternatives that require less dynamic signage, which may use messages on DMS instead of overhead lane control signs or longer-distance intervals between gantries. Can dynamic information traditionally presented on lane control signs with supplemental DMS be presented on less signage in an equally or more effective manner? This may examine dynamic lane control, dynamic speed limits, or dynamic queue warnings as currently presented in urban areas on multipurpose overhead lane control signs, as seen in the photo below. (Q4) 7. Given the many variations in signage for dynamic speed limit deployments, what information and display for dynamic speeds is most effective for achieving driver understanding and reduced speeds? This may identify different approaches for advisory and regulatory speeds, different conditions, e.g., weather, work zones, and recurring congestion, and includes provision of static signs and supplemental information regarding the cause for a reduced speed, and consideration of a fully dynamic sign versus a sign with only dynamic digits. (Q4) 8. Is there a way to accurately quantify mobility-related benefits of an ATM deployment, or the safety-related benefits of a temporary ATM deployment? (Q5) 9. How can agencies systematically trade-off the various criteria associated with mobility, safety, cost, and driver needs when considering the deployment of ATM strategies? This question examines how agencies determine driver needs: what is accepted and will be used to inform travel choices, to justify the costs of investing in ATM strategies. (Q6) 10. Given a situation where multiple ATM media are available, what information do drivers want/how do drivers want to receive the information/when do drivers want to receive the information? This question focuses on drivers’ subjective

44 preference without considering drivers’ performance or objective outcomes. Among the various ATM strategies, drivers’ preference regarding queue warning information will be asked (i.e., information type x ATM media x information receiving timing). (Q1) 11. Given a situation where multiple ATM media are available, what would be the most efficient and the least distracting modality (or modality combination) to deliver ATM information for the alternative/innovative ATM media? Especially for the alternative ATM media such as smart phones and in-vehicle displays, ATM information can be delivered by multiple modalities (e.g., auditory messages, visual messages, or combination of two). By utilizing previous guidelines (e.g., Campbell et al., 2016), which suggested how to select sensory modalities based on message complexity, receiving locations, information priority, etc., this question will examine the most efficient and the least distracting modality for the alternative ATM media when the ATM messages are available from both the alternative media (i.e., in the vehicle) and traditional electronic signs (i.e., outside of the vehicle). (Q2) 12. In the previous research, none of the reviewed studies deeply addressed integrated applications where both traditional ATM and alternative media (e.g., in-vehicle displays) are employed together. In a situation where multiple ATM media are deployed (e.g., electronic signs and in-vehicle displays), should they deliver the same information? Or should each medium need to play a specific role to compensate each other and to avoid redundancy? And what will be the best way to harmonize multiple ATM media (including traditional and alternative media) and how to evaluate the effectiveness/efficiency? (Q3) 13. There are available guidelines of ATM messages for the traditional media (e.g., electronic signs) and also available guidelines of general driver-vehicle interface (DVI) topics. However, little to no research is available regarding structuring ATM message content (and symbols) for portable electronic devices/in-vehicle displays/mobile. What kind of ATM strategies/messages is practically feasible for shifting to smart phone applications/embedded in-vehicle displays? And which currently available guidelines can be used for this transition? And what are the gaps between currently available guidelines and requirements for presenting/formatting/prioritizing ATM messages on alternative media? (Q4) After identifying the 13 research gaps, three experts rated each gap along a five-point scale on three criteria: “Relevance,” “Usefulness,” and “Expected cost.” These criteria reflected the overall project goals related to ATM strategies and guideline development, and the types of studies could be accomplished within the scope of this project (see Table 10). The selected research approaches reflected a balance between technical, practical, schedule, and cost factors (e.g., while a driving simulator may be the best tool for some gaps, the expense limits its practicality). The values of 1 through 5 (in 0.5 increments if necessary) were used to quantify the merit of each research gap along each scale. For the “relevance” and “usefulness” scales, higher values reflect a higher degree of relevance/usefulness. Note that these types of scales can be highly subjective and the boundaries between rating categories is not always clearly apparent.

45 Table 10: Definitions for rating within the three scales. 1. Relevance to ATM Project Objectives: The extent to which the research question addressed the stated project objectives and other related issues. 5. Most Relevant 4. 3. Moderately Relevant 2. 1. Not Specifically Relevant Topic research addresses multiple, high value, Tier 1 objectives Topic research addresses a single Tier 1 objective, or multiple Tier 2 objectives Topic research addresses a single Tier 2 objective Topic research addresses key issues that are indirectly related to project objectives, or are other, relevant, related issues Topic research is not specifically relevant to effective ways to disseminate ATM information but relates to information that could be extrapolated to general ATM systems 2. Usefulness to Design Guideline Development: The extent to which answering the research question would provide information that directly supports guideline development. 5. Empirical Guideline(s) 4. 3. Applicable Data/Info 2. 1.Basic research Topic research on its own will directly support the development of a complete guideline based almost entirely on empirical data Topic research will produce sufficient data/information that will enable the development of some general guidelines Topic research will produce some data, information/analysis that when combined with expert judgment will produce guidelines Topic research will yield guidelines based on expert judgment in combination with human factors principles Topic research will produce basic research findings that, while interesting, will not immediately lead to guidelines Provides clear guidance that stands on its own Provides clear guidance, but will need to be paired with other data to form a guideline Provides relevant performance data that requires the input of expert judgment General principles, analytical work, or research from other domains Basic research 3. Estimated Level of Effort/Cost: The expected labor effort required to conduct the research. 5. Lowest Effort 4. 3. Mid-Level Effort 2. 1.Highest Effort 2 person-weeks (e.g., analytical effort, heuristic evaluation, short literature review/synthesis) 8 person-weeks (e.g., task analysis or kinematic analysis of 2-4 scenarios, short in- lab study without development) 16 person-weeks (e.g., small focus group, in-lab study with development, task analysis or kinematic analysis of 5- 10 scenarios) 32 person-weeks (e.g., large focus group, series of in-lab studies, simulator study with simple scenario development.) Methodology schedule/budget matches or exceeds that planned for the entire project (e.g., field study, simulator study requiring significant development)

46 Table 11. List of the key research questions and corresponding research gaps. Key research questions in this project Relevant research gaps 1. What information related to ATM strategies does a driver want and need? What characteristics are associated with this information (e.g., reliability, timeliness)? 1, 2, 3, 10 2. How much information can a driver process via the complementary and contrasting modalities (e.g., visual, auditory), given the context and distractions? 1, 4, 11 3. What existing and potential media could be used to deliver this information? Media that are under the control of transportation agencies (e.g., electronic signs) are of primary interest but alternative and innovative media (e.g., in-vehicle displays, cell phone applications, geographic information systems) and their evolving capabilities and roles must be examined. 3, 4, 12 4. Given a particular message and medium, what are effective ways to prioritize, format, and present the information to achieve a desired and safe response by drivers? 4, 5, 6, 7, 13 5. How can an agency evaluate the return on investment of an ATM infrastructure or information technology decision? 8 6. How can an agency balance the needs of drivers and the infrastructure costs, including maintenance and operations? 9 Three experts individually rated each research gap using the scales shown above in Table 10. Prior to conducting the ratings, the experts discussed and agreed upon interpretations of the scales. Ratings from each reviewer were compiled into a spreadsheet. Research gaps with a high variance in any scale were identified, discussed, and rated again. After all ratings were finalized, overall scores were calculated for each research gap (no weighting values were used). Table 12 and Figure 42 show the final scores of the 13 research gaps. Table 12: Final scores for the 13 research gaps. Research gap Relevance Usefulness Cost 1 4.5 4 2.5 2 4 3.5 2 3 5 3.5 3 4 4.5 3.5 1.5 5 4 3 2.5 6 4 3 3 7 3 4 2 8 5 4.5 4 9 5 4.5 4 10 4 4.5 3 11 4 4 2 12 4 4 2 13 4 3 4

47 Figure 42. Final scores of the 13 research gaps in three dimensions (color represents expected methods to conduct studies). Following this initial evaluation of the 13 research gaps, the project team conducted further discussions to decide how to interpret the gaps analysis, prioritize the gaps, and develop more detailed work plans to address them. Also, we had requested ratings and general inputs on the gaps from both the State DOT stakeholder group (see Table 10 above) and the NCHRP project panel. We received some qualitative feedback from several members of the stakeholder group and took these comments into account during our deliberations. Conclusions As seen above in Table 12 and Figure 42, all of the gaps obtained relatively high ratings for both relevance and usefulness. Given the range of costs associated with the gaps, our initial approach was to try and construct a series of studies that – together – would address all 13 of the research gaps. However, we determined that it was premature to address two of the gaps (#7 and #13). Thus, the empirical studies described in the next chapter were designed to address all but these two gaps. 7 14 13 1211 10 65 2 4 1 98 3 1 2 3 4 5 1 2 3 4 5 Relevance U se fu ln es s Method focus group not determined simulator State DOT survey Cost 1.5 2.0 2.5 3.0 3.5 4.0