Who Crossed the Centerline First?

---

A head-on collision occurred between a northbound Toyota SUV and a southbound Chevrolet pickup truck on a two-lane, two-direction roadway.  The driver of the Toyota sustained fatal injuries as a result of the crash.

At the scene, law enforcement documented a gouge mark and associated debris field in the southbound travel lane.  Based on this evidence, investigators concluded that the Toyota had crossed the double-yellow centerline into the path of the Chevrolet, causing the collision.  The criminal investigation was subsequently closed.

The engineers at DJS were provided with the police investigation file, including photographs taken at the scene. Consistent with the police conclusion, the gouge mark and surrounding roadway evidence indicated that the collision had occurred in the Chevrolet’s southbound lane of travel; however, to complete a robust reconstruction of the events leading up to the collision, event data was acquired from the Toyota.

In addition to standard Airbag Control Module (ACM) data, including vehicle speed, accelerator input, braking, and steering information, the subject Toyota was capable of storing Event Data Recorder (EDR)-related images via its built-in dashcam.  This dashcam is part of the Toyota Safety Sense (TSS) system controlling features such as automatic braking, steering assist, and dynamic cruise control.

The Toyota’s ACM data captured an abrupt steering input to the left (toward the oncoming lane) followed by a brief corrective input back to the right just prior to impact.  More importantly, the pre-collision images revealed that, before any steering input from the Toyota driver, the oncoming Chevrolet pickup was traveling directly toward him, with more than half of the vehicle encroaching into the Toyota’s northbound travel lane.  In response to this immediate hazard, the Toyota driver steered left in an apparent evasive maneuver.  Within fractions of a second, the Chevrolet abruptly corrected back toward its proper lane and directly into the Toyota’s new path of travel.   While the ACM data shows that the Toyota driver attempted to once again steer away from the oncoming Chevrolet, the closing speed between the vehicles was too great, and the collision ultimately could not be avoided.

Thorough forensic investigation, requiring evaluation of all available physical evidence, uncovered that the Chevrolet pickup truck had initially crossed the centerline, thus creating a hazard for the northbound Toyota.  The failure of the pickup truck to maintain its travel lane was the precipitating factor which led to the collision.  The Toyota’s movements across the centerline, which were initially deemed the cause of the crash based on the point of impact alone, were made in response to the hazard created by the Chevrolet.  This case underscores how a complete analysis of all available data can reveal critical context by providing insight into pre-impact conditions.