In September of 1979, the National Highway Traffic Safety Administration (NHTSA) passed a bill which stated that all car, pickup truck and motorcycle speedometers were to display a maximum speed of 85 miles-per-hour. This U.S. federal regulation also required speedometers to have a special emphasis on the number 55 (the national speed limit at the time).
Limiting speedometers to 85 mph, even though most cars could go much faster, was in response to America's energy crisis. It was an attempt to slow cars down, and in doing so, save gas.
The speedometer limits certainly didn't govern the speed of the car, and the 85 mph max looked pretty silly on cars like the Delorean, Pantera, and Porsche 928. Some car manufacturers got around the rule by ending the numbers at 85 but leaving lines beyond that to show higher speeds.
In reality, the 85 MPH speedo mandate did little to change the driving habits of most Americans. While government officials hoped gasoline consumption would fall by 2.2%, actual savings averaged less than 1%.
Emergency Highway Energy Conservation Act
Although all U.S. States have control over their own speed limits, the Emergency Highway Energy Conservation Act changed that for awhile. Signed by President Richard Nixon on January 2, 1974, the act prohibited the Federal Highway Administration from approving highway projects in any State having a maximum speed limit over 55 mph.
Any U.S. State could keep higher than 55-mph speed limits if they wanted to, but they would lose Federal-aid highway funding. Naturally, all 50 States complied with the legislation.
The objective of the act was part of a nationwide effort to save fuel and reduce foreign dependency on oil. It was in direct response to oil price spikes and supply disruptions that started from the 1973 oil crisis.
With fewer people driving, government officials started noticing highway deaths dropping and mistakenly associated it with speed. However, there was no proof that the lower speed limit was actually a factor.
The mandatory 55 mph limit was widely disregarded by motorists, with many states opposing the law. Congress repealed the Act in 1995, returning speed limit settings to individual state governments.
The 85 mph speedometer mandate ended in 1981 after much debate and little proof it actually did anything to change driver behavior. President Ronald Reagan, who campaigned on a pledge to end excessive government regulation, helped repeal the law. There has never been any data showing that the 85 mph speedometer saved lives.
Porsche was one of the first manufacturers to switch back, offering recalibration and retrofit dials for their cars produced during 1979-1982.
Many cars kept 85 mph speedometers for several years until they were redesigned. A mid-80s Buick Riviera with full digital dash would flash "85-85-85" when exceeding that speed, despite having the extra "1" for the hundreds digit (necessary for kilometers). By the late eighties, most cars were back to 120 mph speedometers. Today, speedometers routinely go to 160 mph, even though the maximum speed limit is less than half that.
