Understanding Contributing Factors to Wrong-way Crashes and Evaluating the Effectiveness of Countermeasures in Reducing Wrong-way Crash Risk of Older Drivers

Although relatively infrequent, when Wrong Way Crashes (WWCs) occur they are much more likely to be fatal, and to involve multiple fatalities, compared to other types of highway crashes. Impairment as a result of drug and/or alcohol consumption is a major contributing factor to WWCs. However, older drivers are also at greater risk of being involved in WWCs. The focus of the current project was assess the effectiveness of different countermeasures in preventing Wrong Way Entries (WWEs), a frequent precursor to WWCs, and reducing confusion regarding highway entry points. A driving simulator study asked older drivers (65+) to enter a highway using an entrance ramp on the left while passing an exit ramp on the left that featured various levels of wrong way countermeasures (minimum required signs and pavement markings defined by the MUTCD, minimum plus the addition of a No Left Turn (R3-2) sign before the lip of the exit ramp, and an enhanced countermeasure condition that included additional signs, larger signs, and enhanced pavement markers. The number of WWEs did not statistically differ as a function of countermeasure level, nor did pre-planned analyses of behavioral driving data reveal differences in uncertainty regarding which ramp (entrance or exit) to enter. Exploratory analyses found that a measure of confusion/uncertainty (speed before the exit ramp) did differ significantly between the minimum and enhanced countermeasure conditions, in line with previous simulator findings that enhanced countermeasures can reduce confusion (Boot, Charness, Mitchum, Roque, Stothart, & Barajas, 2015). While providing some support for the benefit of enhanced countermeasures, results also suggest that WWEs are particularly difficult to prevent. Even in the minimum plus and enhanced conditions featuring multiple redundant cues, some older drivers (2) still entered the exit ramp. This research highlights the need to understand not only the best set of cues to prevent WWEs, but the most effective cues to provide further down the exit ramp (e.g., flashing Wrong Way signs, flashing in pavement LED markers) to encourage retreat once a WWE has occurred.