Impact of Retroreflective Backplates and Flashing Yellow Arrows on Distraction Crashes in Kentucky

This study investigates the safety effectiveness of retroreflective backplate (RRB) and left-turn flashing yellow arrow (LFY) on distraction-related crashes in Kentucky through a before-and-after analysis. A sample of 35 and 72 signalized intersections (mostly 4-legged) in Kentucky installed with each of the RRB and LFY countermeasures, respectively, were used. Before-and-after distraction-related crash records at these intersections were obtained from the Kentucky Transportation Cabinet (KYTC). For both RRB and LFY countermeasures, typical three crash years in each of the before-and-after periods were used. In addition, the geometric characteristics and annual average daily traffic (AADT) on both major and minor intersecting approaches were collected manually by the research team and integrated with the crash database. To quantify the safety effectiveness of the installed countermeasures, crash reduction factors (CRFs) and equivalent property damage only (EPDO) rates were used. The EPDO rate method was used since it accounts for traffic exposure. The CRF and EPDO rates were estimated at different crash injury severity (KABCO) levels and time of the crash (peak morning “7:30 am to 9:59 am”, off-peak morning “10:00 am to 3:29 pm”, peak afternoon “3:30 pm to 6:59 pm”, and off-peak night/dawn “7:00 pm to 7:29 am”). The results showed that fatal and injury distraction-related crashes significantly declined by 23% and EPDO rates declined by 13% post RRB installations. Furthermore, RRBs were highly effective in reducing distraction-related crashes during peak morning (46%) and off-peak night/dawn (24%). Surprisingly, post LFY installation, distraction-related crashes significantly increased by 62.5%, 40%, and 6.5% for severity levels K, B, and C, respectively. Furthermore, LFYs were found to increase the EPDO rates for peak morning (4.5%), off-peak morning (8.2%), and off-peak night/dawn (86.5%), possibly due to the inability of distracted drivers to correctly judge available gaps and yield safely. Overall, the before-and-after analyses suggested that RRB was more effective than LFY in reducing distraction-related crashes at signalized intersections.