The Hazardous Materials Transportation Act was passed by the U.S. Congress in 1975.  It was part of a general transportation law, and it strengthened previous laws of its kind. 

It was passed as a reaction to increasing illegal dumping of chemicals.  This dumping began when many landfills stopped accepting hazardous materials; with few cheap alternatives and lax law enforcement, illegal dumping had become common: waste was disposed of anywhere from abandoned lots to public highways.  In fact, according to the U.S. Department of Transportation, 75 percent of all transported materials violated regulations.  Stronger enforcement and regulations were necessary.

The 1975 law put in place many chemical transportation standards. Materials that fall under this law are those classified as hazardous by either the Resource Conservation and Recovery Act or the Environmental Protection Agency.  Transporters are required to register with state and federal agencies, must record pick-ups and deliveries, may only deliver to permitted facilities, and must report and clean-up any spills or discharges that occur.  The states are given room to set regulations, but only within limits. Hazardous transportation vehicles must have a sign identifying their loads and must  provide other information at various stages.

Major amendments were added to the Act in 1990 in the form of the Hazardous Materials Transportation Uniform Safety Act.  This Act made an attempt to strengthen the enforcement of the original law by increasing inspector numbers, tightening penalties, and offering accident response aid to states.