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.
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.
Hours-Of-Service U.S. and
Canada have set rules that govern the hours of service
of commercial vehicle drivers engaged in interstate
and international trucking operations.
Hydroplaning When the tires
lose contact with a wet road surface.