Investigating the effects of left-turn distracted drivers on signalized intersections’ traffic operations

Abstract

Distracted driving represents a serious obstacle to maintaining an efficient transportation system. The safety impacts of distracted driving had been thoroughly explored. However, the traffic operations impact has received less attention. Few studies addressed distracted driving behaviors in through lanes, but less focus has been provided on the left turners. The goal of this study is to fill this gap in the research and address the impact of distracted driving for left turners on traffic operations at signalized intersections. Field data were collected from six (6) intersections, with thousands of observations analyzed in Orange County, Florida, studying different land use, lane configurations, and peak periods. The results demonstrated that 87% of all drivers were distracted. 28% were distracted by cell phone usage and showed significant effect only during the AM peak. During the PM peak, talking to passengers and dashboard categories were significant. In all peak periods, the category of “not identified” distractions was dominant (48%), indicating drivers not paying attention and staring through the windshield. Drivers in the first row in the queue experienced more distractions in the PM peak than in the AM peak. Motorists in residential & school land use had lower headway than those in mixed land use. This can be attributed to motorists' cautious driving behavior due to the existence of school zones and pedestrian crossings. In contrast, motorists in mixed land use tend to be more distracted by the commercial and tourist areas. The statistical models demonstrated that the overall effect of distracted drivers in the left lanes on the discharge headway at signalized intersections is significant. The TOD analysis showed that the distractions increased the headway by 40%, 37%, and 43% during the AM, MD and PM peak hours, respectively. Conversely, the overall distractions model results showed that the base headway increased by 40% resulting in reducing the intersection’s capacity by 30%.