Fatigue, Impairment & Dangerous Behavior

Three physical realities amplify the consequences. First, there’s stopping distance. A loaded tractor-trailer traveling at 65 mph requires approximately 525 feet to stop, and that distance grows with the square of the speed. Second, there’s vehicle stability. Trucks have a higher center of gravity, making them more susceptible to rollover during emergency maneuvers at elevated speeds. Third, there’s crash energy. Because kinetic energy scales with the square of velocity, even modest speed increases for an 80,000-pound vehicle produce enormous increases in destructive energy.

A speed limiter is relevant in litigation in two ways. If the truck was equipped with a limiter and the ECM data shows the truck exceeded the limiter’s set speed, the data indicates the limiter was disabled, bypassed, or malfunctioning, raising questions about tampering and carrier monitoring. If the truck lacked a speed limiter despite the carrier’s knowledge that its drivers routinely exceeded posted limits, the absence of a limiter becomes evidence that the carrier had a technologically available means of preventing speeding and chose not to use it.

Carrier liability arises through multiple pathways. The most direct is respondeat superior, or vicarious liability for the driver’s negligent operation within the course and scope of employment. Additionally, a carrier that knew or should have known a driver was habitually speeding and took no corrective action may face a negligent retention claim. Evidence supporting these claims comes from telematics data showing repeated speed violations, CSA scores, dispatch records showing delivery windows incompatible with legal driving speeds, and compensation structures that incentivize speed over compliance.

The engine control module (ECM) in a commercial truck records vehicle speed continuously, creating a second-by-second record of how fast the truck was traveling. The ECM data captures the actual speed of the vehicle at each second of the recorded interval; it is a measurement, recorded by the vehicle’s own electronic system, timestamped to the second. The data also reveals pre-impact behavior: whether the driver was accelerating or decelerating, whether cruise control was engaged and at what speed, and when the brake was first applied.