What do drivers do when they turn left? 

Kineticorp Forensic Animator, Neal Carter, discusses our latest research “Lateral and Tangential Accelerations of Left Turning Vehicles from Naturalistic Observations.” Neal presented the findings at SAE International‘s 2019 World Congress Event (WCX). A special thanks to Steve Beier and Rheana Cordero for their involvement with the project.

Publication Introduction:

When reconstructing collisions involving left turning vehicles at intersections, accident reconstructionists are often required to determine the relative timing and spacing between two vehicles involved in such a collision. This time-space analysis frequently involves determining or prescribing a path and acceleration profile for the left turning vehicle. Although numerous studies have examined the straight-line acceleration of vehicles, only two studies have presented the tangential and lateral acceleration of left turning vehicles. This paper expands on the results of those limited studies and presents a methodology to automatically detect and track vehicles in a video file. The authors made observations of left turning vehicles at three intersections. Each intersection incorporated permissive green turn phases for left turning vehicles. The authors recorded video of left turning vehicles at each intersection from a small unmanned aerial system (sUAS), and that video was analyzed with a convolutional neural network designed to detect vehicles. The detected vehicles were then tracked over time and the results were analyzed. A total of 86 left turning vehicles were analyzed. In 23 of the observed turns, an oncoming vehicle was also visible in the video. The spatial relationship between the oncoming vehicles and the left turning vehicles was analyzed and the relationship between gap acceptance and acceleration is presented. Accident reconstructionists and traffic engineers can use this data to prescribe realistic values or ranges to accelerations of left-turning vehicles… Purchase Full Publication

Full Publication:

SAE 2019-01-0421 – Lateral and Tangential Accelerations of Left Turning Vehicles from Naturalistic Observations


Neal Carter, Steven Beier, Rheana Cordero

Related Case Studies, Content & Research:

SAE 2019-01-1005 – Nighttime Visibility in Varying Moonlight Conditions

SAE 2017-01-1366 – Comparing a Timed Exposure Methodology to the Nighttime Recognition Responses from SHRP-2 Naturalistic Drivers

Collision Magazine, Volume 11, Issue 3, 2016 – How Accurate Are Witness Distance Estimates Given in Car Lengths?

SAE 2007-01-4232 – A Method for Determining and Presenting Driver Visibility in Commercial Vehicles

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