Glossary of Semi Truck Crash Terms

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Hazmat: Hazardous materials, as classified by the U.S. Environmental Protection Agency (EPA). Transport of hazardous materials is strictly regulated by the U.S. Department of Transportation.

Headache Rack: Heavy protective barrier mounted behind the tractor's cab. Designed to prevent "headaches" caused by load shifting forward from the trailer and crushing the cab.

HCFC: Hydrochlorofluorocarbon.

Horsepower (hp): Measure of power (the amount of work that can be done over a given amount of time). One horsepower is defined as 33,000 foot-pounds of work in one minute. Example: Lifting 33,000 pounds one foot in one minute, or lifting 3300 pounds ten feet in one minute.

Horsepower, Gross Laboratory: Tested horsepower of a "bare" engine without fan, water pump, alternator, exhaust system or any other accessories.

Horsepower, SAE Net: Horsepower capability of an engine with full accessories and exhaust system. Test procedures per standards of Society of Automotive Engineers (SAE).

Hours-Of-Service: U.S. Department of Transportation safety regulations which govern the hours of service of commercial vehicle drivers engaged in interstate trucking operations.