ARCCA was asked to investigate a tractor trailer fire that damaged a popular highway. Initially, it was theorized that improper brake service or maintenance was the cause of the fire.
Unless firefighters can get to a scene quickly, the fire patterns on a motor vehicle or truck can be affected by external factors such as weather and wind, or intrinsic factors such as the fuel load and ease of ignition of different parts of the vehicle. In this case, the initial theory was that the brake system failed, resulting in locking of the brakes, skidding and frictional ignition of the tires, which then ultimately spread fire to the trailer.
The inspection revealed that there were conical fire patterns as a result of the subsequent ignition of the tires. But the fire patterns and heat damage on the remaining tires revealed that they were stationary at the time of the fire and were damaged from outboard to inboard. Also, inspection of what remained of the brake system did not support the theory that the brakes were locked or that the brakes were generating enough excessive heat to ignite the tires. The right side of the trailer was far more damaged than the left side.