Summary: The national 55 mile per hour (mph) speed limit law was enacted as a fuel conservation measure after the 1973 Arab oil embargo, and secondarily, to improve highway safety. Its effectiveness was evaluated from Department of Transportation (DOT) information, meetings with law enforcement and highway officials in five states, and discussions with regional safety administration offices.
During the first year, average speeds did drop about five miles per hour, some fuel was saved, and traffic fatalities were reduced. However, when the public felt the energy crisis had abated, speeds increased, and many drivers are now speeding. Fuel savings have proved to be only a small percentage of total gas used. Police enforcement is severely limited by money and staff. The DOT public information campaign had only limited success. Federal involvement in state traffic enforcement is a delicate issue. Still, federal-aid highway construction funds are supposed to be withheld if states do not comply with the 55 mph limit. If this sanction were used, it could have a negative impact on highway safety and conservation, due to state resentment.
