Principles and Guidance for Presenting Active Traffic Management Information to Drivers (2021) / Chapter Skim
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48 Chapter 5: Empirical Studies This chapter describes the methods and finding from three research studies that were conducted to identify the specific research gap identified in earlier project activities. The studies consisted of two driving simulator experiments to examine some of the research gaps involving human factors issues about ATM message dissemination.
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49 General Approach to Experiments 1 and 2 The two experiments conducted to examine human factors issues regarding ATM message dissemination involved data collection in a driving simulator. In both simulator studies, participants drove for about 8 miles in a pre-designed straight four-lane highway.
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50 o average age = 45.33 (SD = 21.23) o n of male participants = 13 o n of female participants = 8 • Experiment 2 (eye-tracking data)
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51 color-coded to indicate travel speed at or below the speed limit in blue, exceeding the speed limit by 10 mph or less in orange, and exceeding the speed limit by more than 10 mph in red. The application read a stream of data sent from the Battelle Driving Simulator.
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52 Figure 44. A screen capture from the smartphone application (Battelle)
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53 Figure 45. Ergoneers head-mounted eye tracker.
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54 two baseline conditions for Experiment 119) before the main drive and also had a short practice drive with the smartphone application across all experimental conditions.
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55 Experiment 1: Evaluating the Effects of Information Availability of Dynamic Lane Control on Driver Behavior and Distraction Overview The literature review found that there has been little to no research involving systematic comparisons of ATM media (including alternative media) in a situation where multiple types of ATM media are deployed and available at the same time.
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56 Driver distraction was measured by applying existing vehicle-industry guidelines for assessing the distraction impacts of in-vehicle devices. Two sets of guidelines were available for this objective.
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57 Methods While details of our general approach are described in the previous section, this section only includes methods specifically applied to Experiment 1. Independent Variable Experiment 1 included two baseline conditions.
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58 o Comparison of ATM applications o Comparison of presentation timing o Effectiveness of provisional signs Road Layout The simulated road layout was designed to require drivers to change lanes according to the lane closure information. For each experimental condition (referred to as a block)
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59 Figure 48. Lane signal symbols.
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60 Results The results section consisted of three subsections: (a) driving measurements, (b)
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61 information from both the smartphone and the gantries significantly decreased percentage of time in merge/close lanes. • Post-hoc contrast testing showed that there was no significant difference between the always-on and just-in-time modes in lane compliance behavior (p = .83)
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62 Figure 53. Glance measurement summary statistics for Experiment 1.
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63 Figure 54. Total glance time to the smartphone in seconds.
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64 Figure 55. Mean glance time to the smartphone in seconds.
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65 42% of the participants thought they totally comprehended signs/symbols used in the junction control application. One possible explanation for this result is that participants exposure to hard shoulder and junction control was relatively low when they were asked how often they see individual ATM applications.
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66 Figure 59. Ratings for level of comprehension of symbols used in each ATM application.
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67 Figure 61. Preference ratings for overhead mounted signs and smartphone ATM applications.
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68 question, which asked about the appropriateness of the presentation duration for the just-in-time mode, around 64% of the participants indicated that timing was appropriate. The result may indicate that participants preferred the always-on mode because they received the ATM information sooner (see Figure 64)
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69 participants' responses as boxplots with median, interquartile range, and 25th and 75th percentiles to represent/compare two response distributions. Figure 65.
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70 Figure 67. Annoyance ratings for sign presentation by smartphone application mode.
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71 Figure 71. Participants' self-reported effectiveness of the provisional signs.
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72 Overall, participants perceived the provisional signs used to alert drivers to speed reductions as (a) moderately to extremely important (77%)
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73 When the ATM information was available from both the smartphone and overhead gantry, there were no significant differences between the always-on and just-in-time mode in terms of percentage of lane compliance. However, in terms of participants' preference measured as by the post-experiment survey, the majority (70%)
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74 In terms of research gaps 123 and 224, the survey data supported that the provision of additional information before reduced speed zones was perceived as highly important and effective. Also, drivers' comprehension of the messages used in the provisional signs was good.
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75 Experiment 2: Evaluating the Effects of Information Modality and Information Type of Dynamic Speed Limit Displays on Driver Behavior and Distraction. Overview Alternative ATM media can leverage unique information display characteristics compared to infrastructure-based ATM media.
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76 Table 16. Data sources for addressing gaps in Experiment 2.
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77 presented on the screen and also the application read out the speed limit (i.e., displaying the current speed limit with auditory message of the speed limit) when the speed limit information was updated.
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78 o Average glance duration to the smartphone • Survey data o Comparison of DMS, overhead signs, and pictograms o Comparison of presentation styles o Preferred ATM medium Road Layout The simulated road layout was designed to require drivers to change their speed according to dynamic speed limit information. For each experimental condition, a total of four overhead ATM signs were presented (i.e., four gantries within one block)
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79 Figure 77. Sample image of dynamic speed limit information presented on gantries for Experiment 2 (Battelle)
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80 effects, but with different orders of levels of the conditions were tested. The first model compared results to the smartphone-only condition and the second model compared results to the gantry-only condition.
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81 Figure 80. Speed exceedance.
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82 The same set of the linear mixed-effect models was applied to two glance measures: total glance time and average duration of glances to the smartphone. In terms of total glance time (see Figure 82)
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83 Figure 82. Total glance time to the smartphone across experimental conditions.
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84 Figure 83. Mean glance time to smartphone across experimental conditions.
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85 Figure 84. Participants' subjective ratings of effectiveness for three types of ATM media.
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86 Figure 85. Participants' ratings for how well three types of ATM media communicate.
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87 with combinations. Results showed that participants rated the overhead gantry as the most effective way to disseminate the ATM information when combinations were not allowed (Figure 86)
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88 Figure 88. Participants' ratings for usefulness and preference between overhead signs and smartphone application as ATM media.
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89 Figure 89. Participants' comparisons of the three ATM presentation modes in Experiment 2.
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90 Figure 91. Participants' preferred way to receive navigation instructions.
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91 presented as visual information (i.e., the visual-descriptive mode) , participants thought using the application was more visually complicated and required more mental effort compared to AV conditions.
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92 Experiment 3: Examining How Agencies Approach the Deployment and Evaluation of ATM Applications. Overview The goal of Experiment 3 was to identify current and best practices used by agencies to effectively deploy and evaluate the potential and realized benefits of various ATM strategies, as well as guidance available to support a transition to innovative, non-traditional media for presenting dynamic information.
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93 Results The findings in Experiment 3 are compiled through interviews conducted in April-May 2017 and more widely distributed surveys with follow-up interviews conducted in July-August 2019. Individuals were identified from agencies that have diverse experiences in deploying ATM strategies.
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94 Objectives for the Study Objective 1: Quantifying ATM Deployment Benefits The first objective of Experiment 3 was to determine how agencies accurately quantify mobilityrelated benefits of ATM deployments, as well as the safety-related benefits of a temporary ATM deployment. Note that quantifying safety benefits of permanent ATM deployments tends to be more straightforward and was therefore not an emphasis for this objective.
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95 completed but before ATM became operational to compare with operations after ATM was initiated. The evaluation included video analysis to identify changes for inadvisable and compliant maneuvers for both lane change behavior and Scott's law, which requires drivers to slow down and move over one lane, if possible, when approaching a stopped emergency vehicle.
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96 Partnership Agreement (FHWA, 2013) included mobility, safety, and exogenous factors analyses on the ATM corridors, exogenous factors pertaining to a major reconstruction project in Minnesota, the initiation of tolling operations on an existing bridge with no change in capacity in Washington state that changed travel patterns, and technology improvements in both corridors make it difficult to isolate the relative benefits and impacts of the ATM strategies.
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97 considered only mobility and safety impacts. Other agencies applied different criteria, depending on the ATM strategy.
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98 • Utah: Utah DOT is mobility based and relies heavily on user costs. Anything can be justified by user costs and delays: if the DOT can increase mobility for taxpayers and citizens, it is supported.
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99 Resource Gaps Stakeholder participants were also asked about the topic areas for which guidelines and resources were lacking and would have been helpful for planning the design and operations of ATM deployments. Full responses can be found in Appendix A
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100 population. However, the DOT does not necessarily expect to be the provider of in-vehicle messages in the long-term as it would be a burden for drivers to download multiple apps from multiple agencies.
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