Fire on an Off Road Utility Vehicle Working in Brush, East Texas (2021)

In 2021 a public land management agency asked us to investigate a fire on one of its side by side utility vehicles in East Texas. The agency is not named.

Fire under the seat on the move

The vehicle was working off road in brush in support of a field crew. Soon after it climbed a creek bank, other workers saw an orange glow underneath it and called out to the driver, who stopped and found fire under the seat. Neither the water tank on the vehicle nor a hand extinguisher put it out, and it burned until only metal was left. The driver had noticed no loss of power and no smell of fuel beforehand.

Covering the evidence

Rain was in the forecast, so the day after the fire we set a canopy over the vehicle to keep the weather off it. A few days later we examined it in place with agency staff, and we looked at two vehicles of the same kind from its fleet for comparison.

Three hypotheses

Electrical. The battery sits under the seat on the right side. In the wiring harness we found a few small spots of arcing and far more melting, with several conductors fused together. Plastic storage bins from under the seat had been pulled out early in the fire and set aside, and they had no heat damage. Had the wiring below them started the fire, the bins would have been heated before anyone reached them, so we concluded the electrical damage was a result of the fire.

Fuel. Nothing of the fuel system survived to examine, and a recall search by vehicle identification number found no safety recalls. Given what the driver reported, a fuel leak was unlikely, but with that much damage it could not be ruled out.

Debris. These vehicles work in mud and brush. Both comparison vehicles carried a heavy buildup of dry vegetation and dirt around the exhaust and under the seats, and the burned vehicle had the same kind of material near its exhaust. Debris against a hot exhaust could not be ruled out as the ignition source.

What the evidence allowed

The fire left no patterns that pointed to a specific area, so we placed the area of origin from the witness accounts: below the driver seat and at the front of the engine compartment. The point of origin, the first fuel ignited and the cause were all reported as undetermined. The debris found on the comparison vehicles is still worth knowing for any fleet that runs in brush. Work vehicle fires like this one fall under vehicle fire investigation.