Evaluation of driver navigational errors and acceptance of a simulated J-turn intersection.

The J-turn intersection is a novel roadway design which decreases the points of conflict at an intersection, by restricting straight crossing and left-turning movements from the minor road across the highway. The novelty of the intersection design may lead to driver errors and dissatisfaction. This study provides an examination of how naïve or first-time drivers may initially navigate J-turns during their first and early exposures to the novel intersection design. Thirty-six participants with limited previous experience and knowledge of J-turns participated in a simulation study to examine their acceptance of J-turns and left turning navigational performance at three simulated J-turn intersections in counterbalanced order, each featuring one of three signage levels. Results revealed participants committed slightly more frequent minor errors (e.g., inefficient lane selection) and significantly more major errors (e.g., missed U-turn) during the first J-turn exposure and these errors tended to decline during subsequent exposures, while moderate severity errors (e.g., risky lane change) slightly increased. Participants' J-turn acceptance significantly declined following simulated driving exposure. The decline in J-turn acceptance was found to be greater among participants who experienced major severity errors; however, more frequent minor errors were associated with increased acceptance. Signage level had little effect on errors, but participants preferred improved signage or on-road markings to guide crossing movements. This work suggests that advanced educational programs and community initiatives should be utilized to prepare drivers for how to navigate J-turns rather than only rely on J-turn exposure to improve driver performance and acceptance.

Task-Relevant Smartphone Messages Within Work Zones: A Driving Simulation Study.

OBJECTIVE: This study explored the impact of in-vehicle messages relative to roadside messages to alert drivers to events within a simulated work zone, in order to determine if these messages can improve driving performance within the work zone. BACKGROUND: Safety risks in work zones are usually mitigated by design standards and clear signage to communicate work zone information to drivers. Due to distraction and other driving task demands, these signs are not always noticed by motorists, nor are they always followed when they are noticed. METHOD: The driving simulation tested drivers in two different types of work zones, shoulder work, and lane closure. Participants drove through these work zones three times, each with different messaging interfaces to communicate hazardous events to the driver. The interfaces included a roadside, portable changeable message sign, a smartphone presenting only auditory messages, and a smartphone presenting audio-visual messages. RESULTS: There was significantly better driving performance on key metrics including lane deviation for the in-vehicle message conditions relative to the roadside signs. Furthermore, drivers directed visual attention toward the roadway for the in-vehicle message conditions relative to the roadside sign condition. CONCLUSION: The results indicate that in-vehicle messaging could provide benefits to primary task performance in driving if the message content is appropriately designed. APPLICATION: The findings provide support for a design framework to support in-vehicle communication to drivers approaching work zones and other environments to safely alert them to hazards.

Characteristics and Risk Factors for Electric Scooter-Related Crashes and Injury Crashes among Scooter Riders: A Two-Phase Survey Study.

Electric scooters (or e-scooters) are among the most popular micromobility options that have experienced an enormous expansion in urban transportation systems across the world in recent years. Along with the increased usage of e-scooters, the increasing number of e-scooter-related injuries has also become an emerging global public health concern. However, little is known regarding the risk factors for e-scooter-related crashes and injury crashes. This study consisted of a two-phase survey questionnaire administered to a cohort of e-scooter riders (n = 210), which obtained exposure information on riders' demographics, riding behaviors (including infrastructure selection), helmet use, and other crash-related factors. The risk ratios of riders' self-reported involvement in an e-scooter-related crash (i.e., any crash versus no crash) and injury crash (i.e., injury crash versus non-injury crash) were estimated across exposure subcategories using the Negative Binomial regression approach. Males and frequent users of e-scooters were associated with an increased risk of e-scooter-related crashes of any type. For the e-scooter-related injury crashes, more frequently riding on bike lanes (i.e., greater than 25% of the time), either protected or unprotected, was identified as a protective factor. E-scooter-related injury crashes were more likely to occur among females, who reported riding on sidewalks and non-paved surfaces more frequently. The study may help inform public policy regarding e-scooter legislation and prioritize efforts to establish suitable road infrastructure for improved e-scooter riding safety.

Evaluation of the efficacy of an intersection conflict warning system at two-way stop-controlled rural intersections: difference-in-differences and triple-difference analytical approaches.

OBJECTIVE: Intersection conflict warning systems (ICWSs) have been implemented at high-risk two-way stop-controlled intersections to prevent right-angle crashes and associated injuries. This study involved investigation of the impacts of ICWSs on crash reductions. METHODS: The study used a quasi-experimental design to analyse the potential causal relations between Minnesota's ICWSs and various crash rate outcomes (including total, injury, non-injury, targeted right-angle and non-right-angle crashes) in pre-post analyses. A restricted randomisation method enabled identification of three controls to each ICWS treatment intersection, and included as many comparable intersection characteristics as possible. Annual crash rates (per year per intersection) were analysed over the same periods before and after system activation for treatment and control intersections in each matched group. Pre-crash data for 3 years and post-crash data for up to 5 years were included, ranging from 2010 to 2018. Negative binomial regression models with generalised estimating equations were applied to estimate the average, immediate and continuing treatment effects of ICWSs, through the difference-in-differences and difference-in-difference-in-difference approaches, respectively. RESULTS: The ICWS treatment was significantly associated with a decreasing trend for targeted right-angle crash rates posttreatment. Although not statistically significant, most crash rate outcomes appeared to be elevated immediately after treatment (statistically significant for sideswipe crashes only). Pre-post differences in average crash rates (over entire periods), except for incapacitating injury-related crashes, were not statistically significant between treatment and control intersections. CONCLUSIONS: The study provided important insight into potential causal associations between intersection safety countermeasures and crashes at high-risk rural two-way stop-controlled intersections.

Design and evaluation of a rural intersection conflict warning system and alternative designs among various driver age groups.

Advanced Rural Intersection Conflict Warning Systems (RICWS) were deployed as countermeasures to reduce severe right-angle crashes at rural thru-STOP controlled intersections across the United States (U.S.). The simulator study designed and evaluated alternative RICWS designs to existing RICWS interventions, in varying rural driving scenarios, across age groups (N = 40 novice teenage, 40 middle-aged, and 40 older drivers). Each participant was randomly assigned to a RICWS design, either the original or an alternative, and drove through sequences of 17 thru-STOP controlled rural intersections (nine RICWS intervention and eight control intersections). Drivers' gap acceptance performance, intersection driving performance, traffic violation behaviors and self-reported workload were evaluated between intervention and control intersections. Regression models, applying the Generalized Estimating Equation (GEE), enabled efficacy determination of each RICWS design and an aggregated RICWS intervention effect, averaged across all simulated RICWS designs, among different levels of moderating factors. The safety performance and possible risks associated with the use of different RICWS designs were identified. Specifically, the original RICWS design had a significantly greater risk of STOP-sign violations at clear-view intersections with low traffic volumes, compared with control intersections (Risk Ratio = 2.18, 95% CI = 1.03 to 4.64). Except for Alternative RICWS Design 1, the alternative RICWS designs did not appear to outperform the Original RICWS Design. The moderating effects of drivers' ages and intersection types on aggregated RICWS intervention effects were also examined. This study provides important safety implications for development and evaluation of intelligent intersection warning systems, targeted to vulnerable driver populations at high-risk rural intersections.