While the brake systems are being modified, M939 operators will be told to limit vehicle speeds to 40 mph, Taube said. At that speed, he said, operators will be able to safely drive the truck until ABS is added. All Army trucks meet Department of Transportation and federal motor vehicle brake standards in effect at time of manufacture, said Dennis Mazurek, deputy project manager for medium tactical vehicles, for the Army's Program Executive Office for ground combat and support systems. Mich. Mazurek noted that an air-brake system without ABS is very sensitive to driver input and requires some training to operate effectively. Most of the accidents involving the M939 involved panic stopping with the truck sliding and the operator losing control.
Commercial drivers receive extensive training and certification to use air brakes.
Private-sector truckers are also usually more experienced than Army drivers. Some soldiers who drive M939s may not be truck drivers by trade, Mazurek said. Soldier-drivers could be cooks, supply personnel or in other military occupation specialties, he said.