Implications of Distracted Driving on Start-Up Lost Time for Dual Left-Turn Lanes

Abstract

Previous research has found that distracted driving measurably increases driver response times to unanticipated roadway hazards. These instances are of particular consequence as they tend to be highly correlated with vehicle crashes resulting in property damage and/or injury. However, comparatively little attention has been allocated to quantifying the negative impacts of distracted driving on driver reaction to anticipated stimuli. This study empirically determined the impact of distracted driving on queue discharge rates at signalized intersections with protected left-turn phases for dual left-turn lanes. Observational studies were conducted at 11 intersection approaches at six signalized intersections in three states resulting in the observation of 844 distracted and 3,726 undistracted left-turning drivers. A statistical model was developed for the start-up lost time resulting from the average headways of the samples in each state. The difference in start-up lost times between queues comprised entirely of distracted or undistracted drivers ranged from 3.36 to 4.06 s in Kansas, 2.97 to 4.41 s in Oregon, and 2.25 to 5.14 s in Utah.