Girish Mahajan (Editor)

National Maximum Speed Law

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National Maximum Speed Law

The National Maximum Speed Law (NMSL) in the United States was a provision of the Federal 1974 Emergency Highway Energy Conservation Act that prohibited speed limits higher than 55 miles per hour (90 km/h). It was drafted in response to oil price spikes and supply disruptions during the 1973 oil crisis.


While Federal officials hoped gasoline consumption would fall by 2.2%, actual savings were estimated at between 0.5% and 1%.

The law was widely disregarded by motorists, and some states opposed the law, but many jurisdictions discovered it to be a major source of revenue. Actions ranged from proposing deals for an exemption to de-emphasizing speed limit enforcement. The NMSL was modified in 1987 and 1988 to allow up to 65 mph (105 km/h) limits on certain limited access, rural roads. Congress repealed the NMSL in 1995, fully returning speed limit setting authority to the states.

The law's safety benefit is disputed as research found conflicting results.


Historically, the power to set speed limits belonged to the states. Immediately before the National Maximum Speed Law became effective, speed limits were as high as 75 mph (120 km/h). (Kansas had lowered its turnpike speed limit from 80 before 1974.) Montana and Nevada generally posted no speed limits on highways, limiting drivers to only whatever was safe for conditions.

1973—55 mph National Speed Limit

As of November 20, 1973, several states had modified speed limits:

  • 50 mph (80 km/h): Rhode Island, Maryland, Massachusetts, New Jersey, New York, Vermont, and Washington
  • 55 mph (90 km/h): North Carolina and Oregon
  • California lowered some 70 mph (115 km/h) limits to 65 mph (105 km/h).
  • In late November 1973, Texas Governor Dolph Briscoe recommended adoption of a 55 mph (90 km/h) statewide limit. On December 4, the Texas Highway Commission, with a 3–0 vote, adopted this 55 mph (90 km/h) speed limit, citing unsafe speed differentials between the flow of traffic and people driving too slowly to comply with President Nixon's and Governor Briscoe's requests for voluntary slowdowns. The legality of the measure was questioned, and two Texas legislators threatened to sue to block the limit. However, by December 6, Texas Attorney General John Hill ruled that the speed reduction "'was in excess' of the commissioners' legal power," citing that a 1943 Texas Attorney General's opinion held that the legislature holds the power to set the statewide speed limit and the Commission's authority was limited to changing it in specific locales where safety factors required lower limits.
  • As an emergency response to the 1973 oil crisis, on November 26, 1973, President Richard Nixon proposed a national 50 mph (80 km/h) speed limit for passenger vehicles and a 55 mph speed limit for trucks and buses. That, combined with a ban on ornamental lighting, no gasoline sales on Sunday, and a 15% cut in gasoline production, were proposed to reduce total gas consumption by 200,000 barrels a day, representing a 2.2% drop from annualized 1973 gasoline consumption levels. Nixon partly based this on a belief that cars achieve maximum efficiency between 40 and 50 mph (65 and 80 km/h) and that trucks and buses were most efficient at 55 mph (90 km/h).

    The California Trucking Association, the then-largest trucking association in the United States, opposed differential speed limits on grounds that they are "not wise from a safety standpoint."


    The Emergency Highway Energy Conservation Act was a bill in the U.S. Congress that enacted the National Maximum Speed Law. States had to agree to the limit if they desired to receive federal funding for highway repair. The uniform speed limit was signed into law by President Nixon on January 2, 1974, and became effective 60 days later, by requiring the limit as a condition of each state receiving highway funds, a use of the Commerce Clause of the United States Constitution.

    The legislation required 55 mph (90 km/h) speed limits on all four-lane divided highways unless the road had a lower limit before November 1, 1973. In some cases, like the New York Thruway, the 50 mph (80 km/h) speed limit had to be raised to comply with the law. The law capped speed limits at 55 mph (90 km/h) on all other roads.

    A survey by the Associated Press found that, as of Wednesday, January 2, 1974:

  • 12 states already had maximum speed limits of 55 mph (90 km/h).
  • 9 states had maximum speed limits of 50 mph (80 km/h).
  • 29 states had lower limits.
  • This includes some states that voluntarily lowered their limits in advance of the federal requirement.

    On May 12, 1974, the United States Senate defeated a proposal by Senator Robert Dole to raise the speed limit to 60 mph (95 km/h).

    Safety impact

    The limit's effect on highway safety is unclear. During the time the law was enacted and after it was repealed automobile fatalities decreased, and this was widely attributed mainly to automobile safety improvements, owing to an increase in the safety of cars themselves. This decrease in fatalities from automobile accidents makes figuring out the actual impact of the law difficult.

    According to the National Research Council, there was a decrease in fatalities of about 4000 lives in the first year after the law took effect. Later, the National Academies wrote that there is "a strong link between vehicle speed and crash severity [which] supports the need for setting maximum limits on high-speed roads," but that "the available data do not provide an adequate basis for precisely quantifying the effects that changes in speed limits have on driving speeds, safety, and travel time on different kinds of roads." The Academies report also noted that on rural interstates, the free-flowing traffic speed should be the major determinant of the speed limit, because "Drivers typically can anticipate appropriate driving speeds." This is due, in part, to the strong access control in these areas but also is an acknowledgement of the difficulty of enforcing speed laws in these areas.

    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. After the oil crisis abated, the NMSL was retained mainly due to the possible safety aspect.

    Insurance Institute for Highway Safety workers wrote three papers that argue that increase from 55 to 65 mph (90 to 105 km/h) on rural roads led to a 25% to 30% increase in deaths (1/3 from increased travel, 2/3 from increased speed) while the full repeal in 1995 led to a further 15% increase in fatalities. In contrasting work, researchers at University of California Transportation Science Center argue that the interstates in question are only part of the equation, one also must account for traffic moving off the relatively more dangerous country roads and onto the relatively safer interstates. Accounting for this they find that raising rural speed limits to 65 mph (105 km/h) caused a 3.4% to 5.1% decrease in fatalities.

    Fuel savings

    In 1998, the U.S. Transportation Research Board footnoted an estimate that the 1974 National Maximum Speed Limit (NMSL) reduced fuel consumption by 0.2 to 1.0 percent. Rural interstates, the roads most visibly affected by the NMSL, accounted for 9.5% of the U.S' vehicle-miles-traveled in 1973, but such free-flowing roads typically provide more fuel-efficient travel than conventional roads.

    Conservative think tank The Heritage Foundation claims that the United States Department of Transportation's Office of Driver Research found total fuel savings to be 1% and that "independent studies" found a 0.5% savings.

    Opposition and noncompliance

    By the 1980s, traffic surveys showed the NMSL was widely violated::

  • The speed limit had very low compliance, contrary to the commonly accepted engineering practice that says that the speed limit should criminalize only the fastest 15% of drivers:
  • From April through June 1982, speed was monitored on New York's Interstate highways, and an 83% noncompliance rate was found, despite extreme penalties ranging from $100 (1982 dollars, equal to $248 today) or 30 days jail on a first offense to $500 (1982 dollars, equal to $1,241 today), up to 180 days in jail, and a six-month driver's license revocation upon third conviction in 18 months.
  • In the 4th quarter of 1988, 85% of drivers violated the 55 mph (90 km/h) speed limits on Connecticut rural interstates.
  • In 1985, the Texas's State Department of Highways and Public Transportation surveyed motorist speeds at 101 locations on six types of urban and rural roads. It found that 82.2% of motorists violated the speed limit on rural interstates, 67.2% violated speed limits on urban interstates, and 61.6% violated speed limits on all roads.
  • Western states began to reduce fines in the 1980s, effectively minimizing the impact of the 55 mph limit:
  • Arizona, Idaho, Montana, Nevada, and Utah replaced traditional speeding fines with $5–$15 energy wasting fines as long as drivers did not exceed the speed limit in effect before the 55 mph federal requirement.
  • Nevada's energy wasting fine was enacted on April 15, 1981, when signed by Governor Robert List. Motorists not exceeding 70 mph (115 km/h) in 55 mph (90 km/h) zones could be issued $5 "energy wasting" fines. However, standard speeding tickets were still allowed and "troopers were directed not to take the new law as a signal to stop writing tickets".
  • In 1986, North Dakota's fine for speeding up to 15 mph (25 km/h) over the limit was only $15 and had no license points.
  • South Dakota cut speeding fines in 1985 and stopped assessing points for being 10 mph (15 km/h) or less above the speed limit in 1986.
  • On August 1, 1986, Minnesota, which normally suspended licenses after three tickets, stopped counting speeding tickets for no more than 65 mph (105 km/h).
  • In 1981, 33 state legislatures debated measures to oppose the NMSL.
  • Some law enforcement officials openly questioned the speed limit. In 1986, Jerry Baum, director of the South Dakota Highway Patrol, said "Why must I have a trooper stationed on an interstate, at 10 in the morning, worried about a guy driving 60 mph on a system designed to be traveled at 70? He could be out on a Friday night watching for drunken drivers."
  • Even organizations supporting the NMSL, such as the American Automobile Association (AAA) provided lists of locations where the limit was strictly enforced.
  • On June 1, 1986, Nevada challenged the NMSL by posting a 70 mph (115 km/h) limit on 3 miles (5 km) of Interstate 80. The Nevada statute authorizing this speed limit included language that invalidated itself if the federal government suspended transportation funding. Indeed, the Federal Highway Administration immediately withheld highway funding, which automatically invalidated the statute by its own terms.
  • 1987 and 1988—65 mph limit

    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. 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. The program was originally slated to last four years.

    Reclassified roads

    A few roads that weren't Interstate Highways but were built to Interstate standards were redesignated as Interstate Highways to qualify for the increased speed limit:

  • Kansas petitioned the Federal Highway Administration on May 14, 1987, to "designate the turnpike as an Interstate Highway between Topeka and Emporia". This Kansas Turnpike segment had existed since 1956 without a numerical designation. Interstate status was granted, Interstate 335 was designated, and the 65 mph speed limit signs went up.
  • Western Interstate 88 in Illinois had previously been designated as Illinois Route 5.
  • 50 miles (80 km) of the Maine Turnpike between Portland and West Gardiner were designated as Interstate 495 in 1988. The designation for this segment was changed in 2004 to Interstate 95 to simplify the Interstate numbering scheme in Maine.
  • 1995—Repeal of federal limits

    Congress lifted all federal speed limit controls in the National Highway System Designation Act of 1995, returning all speed limit determination authority to the states effective December 8, 1995. Several states immediately reverted to already existing laws. For example, most Texas rural limits that were above 55 mph (90 km/h) in 1974 immediately reverted to 70 mph (115 km/h), causing some legal confusion before the new signs were posted. Montana reverted to non-numerical speed limits on most rural highways, although its legislature adopted 75 mph (120 km/h) as a limit in 1999. Hawaii was the last state to raise its speed limit when, in response to public outcry after an experiment with traffic enforcement cameras in 2002, it raised the maximum speed limit on parts of Interstates H-1 and H-3 to 60 mph (95 km/h).

    Despite the repeal of federal speed limit controls, 2011 maximum speed limits were, on average, lower than in 1974:

  • States with same speed limit as pre-1974: 25
  • States with higher speed limit than pre-1974: 8
  • States with lower speed limits than pre-1974: 17The introduction to 70 or 75 mph speed limits was in effect that year. The introduction to 80 mph limits was in about 2005, and Texas introduced 85 (140) in 2011.
  • Speedometers

    On October 1, 1980, in a regulation that also regulated speedometer and odometer accuracy, the National Highway Traffic Safety Administration (NHTSA) required speedometers to have special emphasis on the number 55 and a maximum speed of 85 mph (137 km/h). However, on October 19, 1980, NHTSA proposed eliminating speedometer and odometer rules because they were "unlikely to yield significant safety benefits" and "[a] highlighted '55' on a speedometer scale adds little to the information provided to the driver by a roadside speed limit sign."

    In popular culture

    The number 55 became a popular shorthand for the 55 mph speed limit. For example, a hand with a pair of fives in Texas hold'em poker is referred to as a "speed limit". Rock musician Sammy Hagar released "I Can't Drive 55", a hit single protesting the rule. The title of Minutemen's critically acclaimed double album Double Nickels on the Dime also refers to it.

    One of a series of advertising campaigns for the 55 mph speed limit offered, "Speed limit 55. It's not just a good idea. It's the law." Intelligentsia riffed that with a more absolute statement based on the speed of light: "186,000 miles per second. It's not just a good idea, it's the law."


    National Maximum Speed Law Wikipedia

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