Speed limits in the United States are set by each state or territory. Highway speed limits can range from an urban low of 35Â mph (56Â km/h) to a rural high of 85Â mph (137Â km/h). Speed limits are typically posted in increments of five miles per hour (8Â km/h). Some states have lower limits for trucks and at night, and occasionally there are minimum speed limits. Most speed limits are set by state or local statute, although each state allows various subdivisions (counties and municipalities) to set a different, generally lower, limit.
The highest speed limits are generally 70 mph (113 km/h) on the West Coast and the inland eastern states, 75â€"80 mph (121â€"129 km/h) in inland western states, along with Arkansas and Louisiana, and 65â€"75 mph (105â€"121 km/h) on the Eastern Seaboard. Alaska, Connecticut, Delaware, Massachusetts, New Jersey, New York, Puerto Rico, Rhode Island, and Vermont have a maximum limit of 65 mph (105 km/h), and Hawaii has a maximum limit of 60 mph (97 km/h). Washington, D.C. and the U.S. Virgin Islands have a maximum speed limit of 55 mph (89 km/h), and Guam and American Samoa have speed limits of 45 mph (72 km/h). Two territories in the U.S. Minor Outlying Islands have their own speed limits: 40 mph (64 km/h) in Wake Island, and 15 mph (24 km/h) in Midway Atoll. Unusual for any state east of the Mississippi River, much of I-95 in Maine north of Bangor allows up to 75 mph (121 km/h), and the same is true for up to 600 miles of freeways in Michigan. Portions of the Idaho, Montana, Nevada, South Dakota, Texas, Utah, and Wyoming road networks have 80 mph (129 km/h) posted limits. The highest posted speed limit in the entire country can be found on the Texas State Highway 130, and it is 85 mph (137 km/h).
For 13 years (January 1974â€"April 1987), federal law withheld Federal highway trust funds to states that had speed limits above 55 mph (89 km/h). From April 1987 through December 8, 1995, an amended federal law disincentivized speed limits above 65 mph (105 km/h).
Overview
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Speed limits
This table contains the most usual posted daytime speed limits, in miles per hour, on typical roads in each category. The values shown are not necessarily the fastest or slowest. They usually indicate, but not always, statutory speed limits. Some states and territories have lower truck speed limits applicable to heavy trucks. If present, they are usually only on freeways or other high-speed roadways. Washington allows for speeds up to 75Â mph (121Â km/h), but the highest posted signs are 70Â mph (110Â km/h). Mississippi allows speeds up to 80Â mph (129Â km/h) on toll roads, but no such roads exist. Oklahoma removed the maximum speed of 75 from its laws, though no road has been posted higher than 75.
History
One of the first speed limits in what would become the United States (at the time, still a British colony) was set in Boston in 1701 by the board of selectmen (similar to a city council):
Ordered, That no person whatsoever Shall at any time hereafter ride or drive a gallop or other extream pace within any of the Streets, lanes, or alleys in this Town on penalty of forfeiting three Shillings for every such offence, and it may be lawfull for any of the Inhabitants of this Town to make Stop of such horse or Rider untill the name of the offender be known in order to prosecution
Federal speed controls
In response to the 1973 oil crisis, Congress enacted the National Maximum Speed Law that created the universal 55 miles per hour (89Â km/h) speed limit. Whether this reduced gasoline consumption is debated and the impact on safety is unclear; studies and opinions of safety advocates are mixed.
The law was widely disregarded by motorists, even after the national maximum was increased to 65 miles per hour (105Â km/h) on certain roads in 1987 and 1988. In 1995, the law was repealed, returning the choice of speed limit to each state.
Upon that repeal, there was effectively no speed limit on Montana's interstates for daytime driving (the nighttime limit was set at 65 mph) from 1995 to 1999, when the state Supreme Court threw out the law as "unconstitutionally vague." The state legislature enacted a 75 mph daytime limit in May 1999.
As of May 15, 2017, 41 states have maximum speed limits of 70 mph or higher. 18 of those states have 75 mph speed limits or higher, while 7 states of that same portion have 80 mph speed limits.
Minimum speed limits
In addition to the legally defined maximum speed, minimum speed limits may be applicable. Occasionally, there are default minimum speed limits for certain types of roads, generally freeways.
Comparable to the common basic speed rule, most jurisdictions also have laws prohibiting speeds so low they are dangerous or impede the normal and reasonable flow of traffic.
Truck speed limits
Some jurisdictions set lower speed limits that are applicable only to large commercial vehicles like heavy trucks and buses. While they are called "truck speed limits", they generally do not apply to light trucks.
A 1987 study said that crash involvement significantly increases when trucks drive much slower than passenger vehicles, suggesting that the difference in speed between passenger vehicles and slower trucks could cause crashes that otherwise may not happen. In a review of available research, the Transportation Research Board said "[no] conclusive evidence could be found to support or reject the use of differential speed limits for passenger cars and heavy trucks" and "a strong case cannot be made on empirical grounds in support of or in opposition to differential speed limits". Another study said that two thirds (67%) of truck/passenger car crashes are the fault of the passenger vehicle.
Night speed limits
The basic speed rule requires drivers adjust speeds to the conditions. This is usually relied upon to regulate proper night speed reductions, if required. Numeric night speed limits, which generally begin 30 minutes after sunset and end 30 minutes before sunrise, are occasionally used where, in theory, safety problems require a speed lower than what is self-selected by drivers.
Examples include:
- Some streets in Tucson, Arizona without street lights.
- Some Florida roads near Southwest Florida International Airport near Cape Coral/Fort Myers. (Most of these roads are labeled as "Panther Zones" or "Panther X-ing" areas.)
- Daniels Parkway Ext., a four-lane divided highway near SW Florida International Airport with a 50Â mph (80Â km/h) daytime limit, and a night speed limit of 45 miles per hour (72Â km/h) is considered by many to be a speed trap. This road joins neighboring SR 82, a two-lane road with a 60Â mph (97Â km/h) speed limit.
- Colorado Highway 13, with a 65Â mph (105Â km/h) day/55Â mph (89Â km/h) night speed limit beginning 7.1Â miles north of I-70 from north of Rifle to Colorado Highway 64 south of Meeker. Rural Colorado Highway 13 is 55 miles per hour (89Â km/h) at night north of Meeker all the way to the Wyoming state line.
- Highway 20 in Washington state between Twisp and Pateros has a 45mph speed limit due to high numbers of deer (and other wildlife) activity. Deer carcasses can be seen along the road all throughout summer
Some states create arbitrary night speed limits applicable to entire classes of roads. Until September 2011, Texas had a statutory 65Â mph (105Â km/h) night speed limit for all roads with a higher limit. Montana has a statutory 65Â mph (105Â km/h) night speed limit on all federal, state, and secondary roads except for Interstates.
Political considerations
Financial concerns
Traffic violations can be a lucrative income source for jurisdictions and insurance companies. For example:
- Westlake, TX took in $42,000 per citizen over nine years for its speed traps.
- Insurance companies may receive several billions of dollars annually in traffic ticket surcharges.
- A study by the Federal Reserve of St. Louis found that traffic ticket writing increases when government revenue decreases.
- 2008 debates over traffic enforcement in Dallas County, TX involved concerns of lost profits if ticketwriting decreased.
- In Massachusetts, half of the ticket money goes to the police department that writes the speeding ticket, the other half goes to fund the court that convicts the speeder or collects the fine from them.
Thus, an authority that sets and enforces speed limits, such as a state government, regulates and taxes insurance companies, who also gain revenue from speeding enforcement. Furthermore, such an authority often requires "all" drivers to have policies with those same companies, solidifying the association between the state and auto insurers. If a driver cannot be covered under an insurance policy because of high risk, the state will assume that high risk for a greater monetary amount; thus resulting in even more revenue generation for the state.
When a speed limit is used to generate revenue but has no safety justification, it is called a speed trap. The town of New Rome, Ohio was such a speed trap, where speeding tickets raised up to $400,000 per year to fund the police department of a 12-acre village with 60 residents.
Environmental concerns
Reduced speed limits are sometimes enacted for air quality reasons. The most prominent example includes Texas' environmental speed limits.
Definition of speeding
Either of the following qualifies a crash as speed-related in accordance with U.S. government rules:
- Exceeding speed limits.
- Driving too fast for conditions.
Speeds in excess of speed limits account for most speed-related traffic citations; generally, "driving too fast for conditions" tickets are issued only after an incident where the ticket issuer found tangible evidence of unreasonable speed, such as a crash.
A criticism of the "exceeding speed limits" definition of speeding is twofold:
- When speed limits are arbitrary, such as when set through political rather than empirical processes, the speed limit's relationship to the maximum safe speed is weakened or intentionally eliminated. Therefore, a crash can be counted as speed-related even if it occurs at a safe speed, simply because the speed was in excess of a politically determined limit.
- The effective limit may still be too fast for certain conditions, such as limited visibility or reduced road traction or even low-speed truck rollovers on exit ramps.
Variable speed limits offer some potential to reduce speed-related crashes. However, due to the high cost of implementation, they exist primarily on freeways. Furthermore, most speed-related crashes occur on local and collector roads, which generally have far lower speed limits and prevailing speeds than freeways.
Prima facie
Most states have absolute speed limits, meaning that a speed in excess of the limit is illegal per se. However, some states have prima facie speed limits. This allows motorists to defend against a speeding charge if it can be proven that the speed was in fact reasonable and prudent.
Speed limits in Texas, Utah, and Rhode Island are prima facie. Some other states have a hybrid system: speed limits may be prima facie up to a certain speed or only on certain roads. For example, speed limits in California up to 55Â mph, or 65Â mph on highways, are prima facie, and those at or above those speeds are absolute.
A successful prima facie defense is rare. Not only does the burden of proof rest upon the accused, a successful defense may involve expenses well in excess of the cost of a ticket, such as an expert witness. Furthermore, because prima facie defenses must be presented in a court, such a defense is difficult for out-of-town motorists.
Metric speed limits
Though not common in the United States, a speed limit may be defined in kilometers per hour (km/h) as well as miles per hour (mph). The Federal Highway Administration's Manual on Uniform Traffic Control Devices, which provides guidelines for speed limit signage, states that "speed limits shown shall be in multiples of 10Â km/h or 5Â mph." If a speed limit sign indicates km/h, the number is circumscribed and "km/h" is written below. Prior to 2003, metric speed limits were designated using the standard speed limit sign, usually with yellow supplemental "METRIC" and "km/h" plaques above it and below it, respectively.
In 1995, the National Highway System Designation Act prohibited use of federal funds to finance new metric signage.
See also
- Driver License Compact
- Non-Resident Violator Compact
- Solomon curve
- Traffic violations reciprocity
- Transportation safety in the United States
Notes
References
Law Review
- R. A. Vinluan (2008). "Indefiniteness of automobile speed regulations as affecting validity". American Law Reportsâ€"Annotated, 3rd Series. 6. The Lawyers Co-operative Publishing Company; Bancroft-Whitney; West Group Annotation Company. p. 1326.Â
- C. C. Marvel (2010). "Meaning of "residence district," "business district," "school area," and the like, in statutes and ordinances regulating speed of motor vehicles". American Law Reportsâ€"Annotated, 2nd Series. 50. The Lawyers Co-operative Publishing Company; Bancroft-Whitney; West Group Annotation Company. p. 343.Â