Speed limits in the United States by jurisdiction

Speed limits in the United States vary depending on jurisdiction. Rural freeway speed limits of are common in the Western United States, while such highways are typically posted at in the Eastern United States. States may also set separate speed limits for trucks and night travel along with minimum speed limits. The highest speed limit in the country is , which is posted on a single stretch of tollway in exurban areas outside Austin, Texas. The lowest maximum speed limit in the country is in American Samoa.

Alabama In Alabama, it is illegal to drive at a speed that is not "reasonable and prudent" for the current conditions and hazards. Drivers must also not drive so slowly that they impede the flow of traffic. If the speed limit is not otherwise posted, it is: in urban areas on unpaved roads on rural paved county roads on other two-lane roads on four-lane roads on Interstate Highways Trucks carrying hazardous materials are not to exceed .

Although not a statutory default limit, the speed limit is usually in residential areas.

Alaska In Alaska, many of the major highways carry a speed limit, including: A majority of the Parks Highway between Fairbanks and Willow (excepting slower zones through Nenana, Denali Park, Cantwell, and Healy) Most of the Richardson Highway between Valdez and North Pole On the Glenn Highway, the freeway between Wasilla and Anchorage, and most of the west of Glennallen The Seward Highway in Anchorage between 36th Avenue and Rabbit Creek Road, and other non-freeway parts of the Seward Highway south of Bird Point Most of the Alaska Highway between the Canadian border and Delta Junction The Minnesota Drive Expressway features a speed limit, as does the Richardson Highway between Fairbanks and North Pole.

Since the mid-1990s, Alaska's major highways have gradually been upgraded from to or . However, several continue to carry the default speed limit, including: The Sterling Highway The Tok Cut-Off The Haines Highway Portions of the Parks Highway and Seward Highway designated "safety zones" Portions of the Elliott Highway and Steese Highway close to Fairbanks Engineering studies are needed to define which road segments to post a speed limit higher than .

The Dalton Highway and parts of the Elliot Highway are .

Default speed limits in Alaska are: in alleys in a business district in a residential district on other roads The speed limit when towing a mobile home is .

American Samoa

The maximum speed limit in American Samoa is , with in residential areas. The speed limit is the lowest maximum speed limit of any state or permanently inhabited territory. Most areas have a speed limit of .

Arizona The default speed limit outside of "business or residential" districts in Arizona is ; within those districts, the default speed limit is . Specific locations in Maricopa County cities, such as Peoria, Laveen, and Tolleson, often have posted speed limits that may be lower. The default school zone speed limit is , while some may be . Exceeding these limits only in the best of driving conditions is considered prima facie evidence of speeding. Altered speed limits are not prima facie.

The maximum speed limit on Interstate Highways is . This limit may be applied outside of "urbanized areas". However, Interstate 10 near the California border is reduced to . Some portions of Interstate 15 have the same regulations due to sharp curves. There is an exception to urban highway in Casa Grande, with a speed limit of , while other urban highways are capped at . Within "business or residential" districts, exceeding the speed limit by more than is a criminal offense. Within "urbanized areas", speed limit citations are given for "waste of a finite resource". This exception only applies within a threshold. As long as the speed does not exceed , the infraction is not recorded as a traffic violation for the purposes of a point system.

Non-passenger vehicles in excess of , or "vehicles drawing a pole trailer" weighing more than may not exceed unless signs are posted that allow such a speed. Yet this does not differ from the default speed limit, and has the practical effect of requiring extra consideration for posting a standard speed limit sign in excess of . A non-numeric minimum speed limit is incorporated with the basic speed rule in Arizona, which also prohibits speeds higher than would be "reasonable and prudent".

Night speed limit signs are posted on some roads within Tucson city limits that do not have street lights. Examples: Fort Lowell Road from Oracle Road to Country Club Road, 22nd Street from Interstate 10 to Cherry Avenue.

In late 2025, Arizona Representative Nick Kupper introduced HB 2059 into the Arizona House of Representatives. The bill, dubbed the 'RAPID Act', if passed into law, would establish 'derestricted speed zones' with no posted speed limit on certain rural stretches of state and interstate highways across Arizona that meet certain prerequisite conditions.

Arkansas Urban districts are posted at by default. Outside of the municipal limits, two-lane state and federal highways have a speed limit of unless otherwise posted, and 2 lane county roads have a speed limit of unless otherwise posted. In June 2015, the Arkansas Highway Commission authorized the Arkansas Highway and Transportation Department (AHTD) to raise the speed limit on undivided 4 and 5 lane roads from , and divided 4 lane roads from ; these changes affect of Arkansas highways. Furthermore, AHTD has established freeway default speed limits. Along rural freeways, the limit is while suburban freeways are posted at . School zone speed limits apply only when children are present, or when a lighted beacon is on if one is provided, and such speed limits are set at unless otherwise posted. It is fairly common however that schools serving only higher grade levels will not have a school speed limit in rural areas or where such school sits more than off of the highway or street.

On March 16, 2017, the Arkansas House introduced a bill that would allow the state highway commission to increase speed limits up to in rural interstate freeways, upon completion of a "traffic and engineering investigation" and sets rural non-divided highway speed limits to . This bill became law on April 7, 2017, however no highways were immediately given a 75 mph limit.

On April 8, 2019, Act 784 was approved which raises the speed limit to / for trucks weighing more than on all rural freeways effective July 1, 2020. The new law eliminates the requirement that the Highway Commission conduct a traffic study before raising the limit; instead, a study will be required to justify lowering the speed limit.

As of August 5, 2020, new signs are up indicating the speed limit increase from 70 to 75 mph (70 mph for trucks) on I-40 west of Little Rock to the Oklahoma border.

California

Basic speed law California's "Basic Speed Law", part of the California Vehicle Code, defines the maximum speed at which a car may travel as a "reasonable and prudent" speed, given road conditions. The reasonable speed may be lower than the posted speed limit in conditions such as gravel—thus limiting the Assured Clear Distance Ahead (ACDA). See Official Reports Opinions Online See Huetter v. Andrews, 91 Cal. App. 2d 142, Berlin v. Violett, 129 Cal.App. 337, Reaugh v. Cudahy Packing Co., 189 Cal. 335 , and Official Reports Opinions Online Basic speed laws are statutized reinforcements of the centuries-old common law negligence doctrine as specifically applied to vehicular speed. California Vehicle Code section 22350 is typical; it states that "No person shall drive a vehicle upon a highway at a speed greater than is reasonable ... and in no event at a speed which endangers the safety of persons or property".

Speed limits in California are mandated by statute to be set: (1) at or below the 85th percentile operating speed; as determined by a traffic and engineering survey—this is the speed that no more than 15% of traffic exceeds; or (2) the prima facie limits mandated when certain criteria are met as described in the vehicle code. These criteria include school zone, alleyway, and residential area.

If the 85th percentile operating speed as measured by a Traffic and Engineering Survey exceeds the design speed, compulsory legal protection is given to that speed—even if it is unsafe with regard to certain technical aspects such as sight distance. This speed creep may continue until the 85th percentile operating speed is comparable to speed psychologically perceived as uncomfortably hazardous.

The theory behind California's 85th percentile statute is that, as a policy, most of the electorate should be seen as lawful, and limits must be practical to enforce. However, there are some circumstances where motorists do not tend to process all the risks involved, and as a mass choose a poor 85th percentile speed. This rule in substance is a process for voting the speed limit by driving; and in contrast to delegating the speed limit to an engineering expert.

The numerical limit set by Caltrans engineers for speed limit signs, generally found on all non-controlled-access routes, is considered a presumptive maximum "reasonable and prudent" speed.

Many speed limit signs are labeled "maximum speed", usually when the limit is or higher. When the National Maximum Speed Law was enacted, California was forced to create a new legal signage category, "Maximum Speed", to indicate to drivers that the Basic Speed Law did not apply for speeds over the federally mandated speed cap; rather, it would be a violation to exceed the fixed maximum speed indicated on the sign, regardless of whether the driver's speed could be considered "reasonable and prudent".

A driver can receive a traffic citation for violating the Basic Speed Law even if their speed is below the "maximum speed limit" if road, weather, or traffic conditions make that speed unsafe. However, because the Basic Speed Law establishes prima facie limits, not absolute ones, they can also defend against a citation for speeding "by competent evidence that the speed in excess of said limits did not constitute a violation of the basic speed law at the time, place and under the conditions then existing", per section 22351(b) of the California Vehicle Code. Thus, a driver who operates over the speed limit, but less than the usual maximum speed ( for two-lane undivided highways, isn't necessarily violating California's speed laws where the driver's speed was otherwise safe under the circumstances.

Speed limits Rural freeways, such as parts of I-5, I-8, I-10, I-15, I-40, I-205, I-215, I-505, I-580, US 101 (until 2023), CA 14, CA 58, and CA 99 have speed limits. The highest speed limit on I-80 is because it passes almost exclusively through urban and mountainous areas. However, the speed limit on the San Francisco–Oakland Bay Bridge and in San Francisco is only . In downtown Los Angeles, the maximum speed limit is . This includes the entire length of the Pasadena Freeway between Pasadena and downtown Los Angeles, and portions of the Hollywood, Santa Ana, Santa Monica, and Harbor Freeways. The default limit on two-lane roads is . Some two-lane roads can be for some locations in California. However, Caltrans or a local agency can post a speed of up to after an engineering study.

There is a speed limit for trucks with at least 3 axles and all vehicles while towing.

In California, the maximum speed in school zones is , but may only be in effect when children are present within that school zone.

Colorado

The maximum speed limit in Colorado is on rural Interstate highways and the toll road portion of SH 470 (E-470), although Interstate 70 in the Rocky Mountains has a limit because of steep grades and curves and a limit at the east and west ends of the Eisenhower Tunnel. The maximum speed limit on other rural highways is .

There are also basic prima facie speed limits in Colorado.