Even after fuel costs began to decrease over time the law would remain in place until 1995 as proponents claimed it reduced traffic fatalities.

Prior to the NMSL, the sole exception to this occurred during World War II, when the U.S. Office of Defense Transportation established a national maximum "Victory Speed Limit" of 35 miles per hour (56 km/h), in addition to gasoline and tire rationing, to help conserve fuel and rubber for the American war effort.

"[15] The Emergency Highway Energy Conservation Act[16] was a bill in the U.S. Congress that included the National Maximum Speed Limit.

[18] A survey by the Associated Press found that, as of Wednesday, January 2, 1974:[18] That includes some states that voluntarily lowered their limits in advance of the federal requirement.

[20] The 55 mph (90 km/h) National Maximum Speed Limit was made permanent when Congress enacted and President Gerald Ford signed into law the Federal-Aid Highway Amendments of 1974 on January 4, 1975.

Both during the time the law was enacted and after it was repealed, automobile fatalities decreased,[22] which was widely attributed mainly to automobile safety improvements, owing to an increase in the safety of cars themselves, and the passage of mandatory seat belt legislation by all states except New Hampshire from the mid-1980s to the early 1990s.

[27] A Cato Institute report showed that the safety record worsened in the first few months of the new speed limits, suggesting that the fatality drop found by the NRC was a statistical anomaly that regressed to the mean by 1978.

[34][35][36] Despite federal compliance standards mandated by Congress that no more than 50 percent of free-flowing traffic on 55 mph-posted highways exceed 55 mph from 1981 onwards, which required up to a 10 percent reduction in federal highway funding for states in noncompliance,[37] by the 1980s traffic surveys showed the NMSL was widely violated: In the April 2, 1987, Surface Transportation and Uniform Relocation Assistance Act, Congress permitted states to raise speed limits to 65 mph (105 km/h) on rural Interstate highways.

[49] In a bill that passed in mid-December 1987, Congress allowed certain non-Interstate rural roads built to Interstate standards to have the higher speed limits.

As of December 29, 1987, the states of California, Florida, Illinois, Iowa, Kansas, Kentucky, and Oklahoma had applied for and been accepted into this program.

[51][52][53] On the other hand, the new 65 mph speed limit for rural Interstates was welcomed by the California Highway Patrol, National Motorists Association (née Citizens' Coalition for Rational Traffic Laws), a motorists' advocacy group, American Motorcyclist Association, Owner-Operator Independent Drivers Association (OOIDA), the automotive enthusiast magazines Motor Trend, Road & Track, Car and Driver, and the late automotive journalist Brock Yates (1934–2016)--perhaps the most outspoken published opponent of the 55 mph National Maximum Speed Limit.

[54] Under the Intermodal Surface Transportation Efficiency Act of 1991,[55] passed by Congress and signed by President George H. W. Bush on December 18, 1991, the 65 mph speed limit was made permanent for rural non-Interstate highways built to Interstate standards.

As required by ISTEA, they were published in the Code of Federal Regulations 23 CFR Part 1260, but no further action was taken by USDOT against the states for speed limit noncompliance for the last few years the NMSL was still in effect until it was repealed in 1995.

Montana reverted to non-numerical speed limits on most rural highways, but its legislature adopted 75 mph (121 km/h) as a limit in 1999; as a result, according to Insurance Institute for Highway Safety researcher Anne McCartt, "What's impressive is the huge drop in the percent of vehicles going very fast....

[70] Rock musician Sammy Hagar released "I Can't Drive 55", a hit single protesting the rule.

Tim Castleman founder of the Drive 55 Conservation Project discussing the benefits of getting drivers to slow down and observe all speed limits, never exceeding 55 MPH to reduce consumption by 20% to 50%.