Overloading trucks or trailers puts additional strain on the vehicle, particularly the brakes and tires. Towing a trailer with a weight heavier than the towing vehicle will lead to loss of control, especially down hills. Loss of control can lead to a fatal accident. The stopping distance drastically increases with additional weight. The truck drier may misjudge the stopping distance of an overloaded truck or trailer causing an accident.

• The chances of a big truck crash resulting in death and serious injuries increase with each extra ton of weight over the 80,000 lbs. GVW limit in federal law. A big truck weighing even a legal 80,000 lbs. GVW is more then twice as likely to be involved in a fatal crash as a truck weighing about 50,000 lbs. GVW. (University of Michigan Transportation Research Institute, 1988).
• Overweight trucks, particularly 100,000 lbs. GVW trucks, dramatically underpay their fair share of taxes and user fees for the repair of U.S. roads and bridges. By damaging roads, large trucks further degrade highway safety. (U.S. DOT, 1997 and 2000).
• Pavement damage is caused almost entirely by heavy trucks, not by passenger cars. One legal 80,000 lbs. GVW tractor-trailer truck does as much damage to road pavement as 9,600 cars. (Highway Research Board, NAS, 1962).

Several studies over more than 20 years, including a recent white papers by the University of Michigan's Transportation Research Institute (UMTRI) found that increasing the weights of trucks, especially in the existing configurations, increased their crash rates, including fatal crash rates.

The U.S. Department of Transportation's Comprehensive Truck Size and Weight Study, issued in 2000, pointed out that the use of certain combination trucks at higher weights could increase fatal crash involvement rates.