This document reports the results of projects BDK83 977-21 and BDV30 TWO 977-04. The combined project investigated the effectiveness of safety countermeasures designed to protect drivers and pedestrians of all ages at intersections. Specifically, we examined 1) whether there is an advantage associated with special emphasis crosswalks compared to standard crosswalk markings, 2) whether estimates of perception-response time, which partially determine yellow signal phase duration, are sufficiently long to account for age-related changes, and 3) whether Flashing Yellow Arrow (FYA) protected/permissive left-turn (PPLT) displays are easily understood by older adults and whether current tip cards are effective at conveying the appropriate responses to these displays. These issues are especially relevant for the state of Florida, given its large and growing older adult population and the fact that Florida is one of the states with the highest pedestrian fatality rates in the United States. The Florida Department of Transportation (FDOT) will use study results to support the implementation of the Aging Road User Strategic Safety Plan through their Safe Mobility for Life Program. Task 1: To ensure that countermeasures address the needs of all drivers and pedestrians, we included younger (ages 21 to 35), middle-aged (ages 50 to 64), and older adult (ages 65 and older) participants. In order to understand the potential advantage of special emphasis crosswalks, we examined both driver and pedestrian responses to standard and special emphasis markings. This included a laboratory study with eye tracking, an observation study to assess pedestrian and some driver behaviours, and a driving simulator study that evaluated the impact of standard and special emphasis crosswalk markings on drivers’ responses to pedestrians entering the roadway and their allocation of attention. In laboratory tasks, a substantial advantage in recognizing the presence of a marked crosswalk was observed for special emphasis markings compared to standard markings. However, this did not translate to faster/more accurate detection of pedestrians within special emphasis markings in simulated roadway scenes. The observational study did not reveal that pedestrians were more likely to use a special emphasis crosswalk compared to a standard marked crosswalk, though some evidence from survey data collected suggested that pedestrians felt more comfortable within special emphasis crosswalks. Finally, the driving simulator study did not reveal that special emphasis crosswalks had a differential impact on drivers’ behaviour or attention compared to standard markings. In sum, special emphasis markings were easier to detect (especially for older adults, and especially at greater distance), but no observable impact on pedestrian or driver behaviour was observed compared to standard crosswalk markings. Task 2: Task 2 focused on estimating perception-response times to the onset of yellow traffic signals to ensure that perception-response times used in decisions such as setting yellow signal duration accurately account for age-related perceptual and cognitive declines. Goals, Operators, Methods, and Selection rules (GOMS) modelling was used to provide these estimates for younger and older adults, and these estimates were checked against data collected as younger and older drivers responded to yellow signals within a driving simulator. Modelling and experimental data were very consistent: the perception-response times of older adults were between 763 and 803ms longer than those of younger adults. Results suggest that estimates of perception-response time might need to be lengthened to account for age-related slowing. Task 3: Task 3 focused on whether FYA PPLT displays are quickly and easily understood by drivers of all ages. A completed literature review suggested that FYA PPLT displays are effective at improving safety (compared to a circular green for the left turn movement), but these studies have generally included few older adult participants, and have not examined the potential benefit of educational materials to improve FYA comprehension. In a laboratory signal comprehension task it was found that in general, although there were errors in comprehension for all age groups, these errors would likely not be safety critical (i.e., participant assumes FYA indicates that the left-turning driver has right-of-way). Similar results were observed (few errors, no crashes) in a driving simulator study of FYA comprehension. However, an effect of FDOT’s FYA tip card was observed. Consistent with uncertainty regarding what to do, participants who were not exposed to the tip card waited at the intersection significantly longer in response to a FYA signal compared to participants who read the tip card before the driving scenario. This effect was observed for both younger and older drives. Based on these findings, we offer a number of recommendations: 1) At signalised intersections, the current study found no evidence of a significant advantage of special emphasis over standard crosswalk markings, however there could be specific situations not tested in the studies reported here in which special emphasis markings might be advantageous such as mid-block crossings or uncontrolled crossings at intersections. 2) Estimates of a perception reaction time (PRT) to a yellow signal, often assumed as 1 second, may not account for age-related changes adequately. To assist older drivers, this estimate should be increased. At a minimum, we recommend additional study to provide evidence that 1 second is sufficient. 3) Flashing Yellow Arrow (FYA) signals do not appear to be associated with safety-critical errors for younger or older adults. We can recommend their further implementation in the state of Florida as a safety countermeasure. 4) We recommend more active dissemination of FYA educational materials such as FDOT’s FYA Tip Card. Tip cards were found to reduce confusion regarding the meaning of this signal and may increase traffic flow. (Author/publisher)
Samenvatting