Speed limits in the United States

Main articles: Speed limit and Speed limits by country

See also: Speed limits in the United States (rail)

A standard sign indicating a speed limit of 80 miles per hour (mph), a night-time speed limit of 65 mph, and a truck speed limit of 55 mph

A speed limit sign entering a school zone, along with a warning light above

Speed limits in the United States are set by each state or territory. Speed limits in the United States vary according to the type of road and land use. Increments of five miles per hour are used. Additionally, these limits sometimes differ according to the type of vehicle and the time of day. Occasionally there are also minimum speed limits.

Most speed limits are set by the legislatures of states and territories as law statutes. States generally allow a statewide transportation agency and lesser authorities to change speed limits.

For approximately thirteen years, no speed limit in the United States exceeded 55 mph. Prior to that, speed limits were mostly the same as today, but more often higher or nonexistent in rural areas. Montana and Nevada among others previously had no statutory speed limits for cars and motorcycles in certain conditions.

The highest speed limits are usually found in the inland West, and the lowest limits are usually found in the Northeast and insular areas. Some limits fall outside these ranges. For example, some two-lane rural roads in Texas have 75 mph (121 km/h) speed limits, and there are two stretches of Interstate Highway in Texas with a daytime 80 mph (129 km/h) speed limit for passenger vehicles, as well as two stretches in Utah with 80 mph limits being tested as of January 2009. In contrast, the highest speed limit on freeways in Hawaii is 60 mph (97 km/h).

Overview

Speed limits

This table contains the most usual 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.

legend:
freeway: Interstate Highway or other state- or federally-numbered road built to Interstate standards. divided: State- or federally-numbered road, generally with four or more lanes, not built to Interstate standards, but with a median or other divider separating directions of travel. undivided: State- or federally-numbered road, generally with two to four lanes, with no separator between directions of travel. county: County-owned roads that are generally not numbered by the state. urban/residential: Residential streets or business districts . school zone: An area on a street near a school or near a crosswalk leading to a school that has a likely presence of pedestrians.
5 miles per hour (8 km/h) 10 miles per hour (16 km/h) 15 miles per hour (24 km/h) 20 miles per hour (32 km/h) 25 miles per hour (40 km/h)	30 miles per hour (48 km/h) 35 miles per hour (56 km/h) 40 miles per hour (64 km/h) 45 miles per hour (72 km/h) 50 miles per hour (80 km/h) 55 miles per hour (89 km/h)	60 miles per hour (97 km/h) 65 miles per hour (105 km/h) 70 miles per hour (113 km/h) 75 miles per hour (121 km/h) 80 miles per hour (129 km/h)

state or territory	freeway (rural)	freeway (trucks)	freeway (urban)	divided (rural)	undivided (rural)	county (rural)	residential (urban)	school zone
Alabama	70		60	65	55	35-45	25	15
Alaska	65		65	65	65	50	25	20
American Samoa	-	-	-	-	25-30	-	15
Arizona	75		65	65	65	65	25	15
Arkansas	70	65	65	60-65	55
California	70	55	65	65	55-65	55-65	25	25
Colorado	75		55-65	65	65	35-55	25-35
Connecticut	65		45-55	55	55	45	25-40	20
Delaware	65		50-55	55	50		25-35	20
District of Columbia	-	-	50	-	-	-	25	15
Florida	70		60	65	60	55-60	30	10-20
Georgia	70		55-65	65	55	-	30	25
Guam	-	-	-	35-45	35-45	-
Hawaii	55-60		50	45	45	45
Idaho	75	65	65	65	65
Illinois	65	55	55	55-65	55	55	30	20
Indiana	70	65	50-55	60	55	55	20-30
Iowa	70		55-65	65	55	45	25	20
Kansas	70		65	65-70	65	55	30
Kentucky	70		55	55	55	55	25-35	25
Louisiana	70		60	65	55	45	25	20
Maine	65		55	55	55	50
Maryland	65		55-60	55	55			15-25
Massachusetts	65		55	55	55		30	20
Michigan	70	60	70	55	55	55	25	25
Minnesota	70		55-60	65	55-60	55-60	30
Mississippi	70		60-70	65	55		25
Missouri	70		55-65	65-70	55-65			20
state or territory	freeway (rural)	freeway (trucks)	freeway (urban)	divided (rural)	undivided (rural)	county (rural)	residential (urban)	school zone
Montana	75	65	65	70	55-70	55-70	25	15
Nebraska	75		60	65	60-65	50-55	25	25
Nevada	75		65	65-70	55-70	55-70	25	15, 25
New Hampshire	65		55	55	55	35	30	20
New Jersey	65		55	55	45-50	45-50	25	20-25
New Mexico	75		65-75	70	55-65	25-55	25-30	15
New York	65		50-55	55	55	55	30
North Carolina	70		60	55	55		20-35	20
North Dakota	75		55-75	70	65	50-65	15-25	15-25
Ohio	65	55-65	55-65	55-65	55	55	25	20
Oklahoma	70-75		65	70	65	45	25	25
Oregon	65	55	55-60	55	55	55	25	20
Pennsylvania	65		55	65	55	35-45	25-35	15
Puerto Rico	60-65	50-55			45-55	-	25-35	15-25
Rhode Island	65		55	55	50	-	25	20
South Carolina	70		60	60	55	-	30
South Dakota	75		65	65	65	55	25-45	15-25
Tennessee	70		55	65-70	55	35-45	20-45	15-20
Texas	70-80	70	60	70-75	70-75	60	30	20
U.S. Virgin Islands	-	-	-	55	35	-	20
Utah	75		65	65	65		25-35	20
Vermont	65		55	55	50	50
Virginia	65		55-65	55-60	55		25	15-35
Washington	70	60	60	65	65	50-55	25-50	20-25
West Virginia	70		60	65	55
Wisconsin	65		55-65	55-65	55	55	25-35	15
Wyoming	75		60	65	65

legend:
freeway: Interstate Highway or other state- or federally-numbered road built to Interstate standards. divided: State- or federally-numbered road, generally with four or more lanes, not built to Interstate standards, but with a median or other divider separating directions of travel. undivided: State- or federally-numbered road, generally with two to four lanes, with no separator between directions of travel. county: County-owned roads that are generally not numbered by the state. residential: Residential streets. school zone: An area on a street near a school or near a crosswalk leading to a school that has a likely presence of pedestrians.
5 miles per hour (8 km/h) 10 miles per hour (16 km/h) 15 miles per hour (24 km/h) 20 miles per hour (32 km/h) 25 miles per hour (40 km/h)	30 miles per hour (48 km/h) 35 miles per hour (56 km/h) 40 miles per hour (64 km/h) 45 miles per hour (72 km/h) 50 miles per hour (80 km/h) 55 miles per hour (89 km/h)	60 miles per hour (97 km/h) 65 miles per hour (105 km/h) 70 miles per hour (113 km/h) 75 miles per hour (121 km/h) 80 miles per hour (129 km/h)

Examples of related laws

State	Typical Fine	Recklessness threshold or enhanced penalty	Absolute/Prima facie	Ticket Dismissal Options	Point System
Texas	$1-$200 plus court fees. Doubled in active school zone or construction zone when workers are present.	None	Prima facie	Defensive driving (once per year) or deferred disposition (restrictions vary, but generally at least 4 per year), but only valid if: Texas resident, speed < 25 mph above limit and < 95 mph, and not in construction zone where workers are present or active school zone.	Point system is annual surcharge only. No provision for license suspension.
Rhode Island			Prima facie	One dismissal every 3 years for speed 14 mph or less over limit.
Virginia	Up to $250 School zone: up to $250 additional Work zone: up to $500 $100 civil penalty in certain towns	20 mph over limit or over 80 mph or "exceeds reasonable speed".	Absolute		Point system leading to fines, suspension, and mandatory driver education.

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 obstruct the normal 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.

Theory

Because trucks are far heavier than other vehicles, they take longer to stop, are less adept at avoiding hazards, and have much greater crash energy. Therefore, it follows from basic physics that limiting truck speeds could reduce the severity and incidence of truck-related crashes.

However, the research record is mixed. A 1987 study finds 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. Furthermore, in a review of available research, the Transportation Research Board (part of the United States National Research Council) states "[no] conclusive evidence could be found to support or reject the use of differential speed limits for passenger cars and heavy trucks" (page 11) and "a strong case cannot be made on empirical grounds in support of or in opposition to differential speed limits" (page 109).

Two thirds (67%) of truck/passenger car crashes are the fault of the passenger vehicle.

Night speed limits

Night speed limit in the Key Deer habitat on the Florida Keys. Note the nonreflective backing of the day speed limit number. At night only the number on the lower sign is visible in the headlights.

While the basic speed rule, which requires drivers to drive a reasonable and proper speed at all times, is usually relied upon to regulate proper night speed reductions, numeric night speed limits (which generally begin 30 minutes after sunset and end 30 minutes before sunrise, though this may vary by local law) generally may be established on roads where safety problems require a speed lower than what is self-selected by drivers. Exceptionally, Texas is the only state with default arbitrary nighttime speed limits.

Political considerations

Arbitrariness

70 mph limit on Texas Farm to Market Road 50 immediately south of Texas State Highway 21. No matter the road quality, no two-lane road in neighboring Louisiana or Arkansas may have a speed limit higher than 55 mph.

Subjective political influence on speed limits is evident by state-to-state speed limit variances that cannot be empirically justified. Examples include:

• Rural sections of Interstate 84 in Oregon and Idaho have a 10-mph speed limit difference.
• The lowest class of state-maintained, two-lane road in Texas may have a 70 mph speed limit, but a two-lane US highway road built to Louisiana's or Arkansas's highest standards will not have a speed limit over 55.

Fiscal concerns

Traffic violations have proved to be a great source of income for many jurisdictions. As a direct consequence, many state administrations have been reluctant to increase the speed limit on state roads. By keeping speed limits "unreasonably" low, the logical conclusion to this effort is that more motorists will appear to "speed". This gives law enforcement personnel the authority to issue traffic citations and thus improve the ticketing authority's revenue. This policy has rarely been voiced or acknowledged.

As a direct consequence of this, insurance companies have benefited as well. As motorists are charged with speeding violations their drivers licenses are assigned "violation points" (except for drivers licensed in South Dakota and other limited instances, where the law does not assign points for speeding violations). The more points accumulated (or demerited, depending on the system) on a license the more risk an insurance company will associate with the driver. This has a direct consequence of increasing insurance premiums, resulting in greater revenue for the insurance company. Insurance companies rarely compete with each other as their premiums are determined by state guidelines.

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.

Environmental concerns

Reduced speed limits are sometimes proposed for air quality reasons in addition to other environmental concerns, such as to protect wildlife or to curb the use of fossil fuels. Examples include Arizona, Florida, and Texas.

Metric speed limits

File:US metric speed limit.png

The values of metric speed limits in the US are to be circumscribed in accordance with the MUTCD.

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 10 km/h or 5 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.

The 1995 National Highway System Designation Act prohibited use of federal funds to finance new metric signage.

Federal speed controls

National 55 mph limit

Further information: National Maximum Speed Law

In response to the 1973 oil crisis, Congress enacted the National Maximum Speed Law that created the universal 55 mph speed limit.

The law was widely disregarded by motorists, even after the national maximum was increased to 65 mph in 1987 on certain roads. In 1995, the law was repealed, returning the choice of speed limit to each state.

2000s

Two prominent members of the United States Senate have speculated on reimposition of federal speed limit controls.

In 2006, Senator Hillary Clinton publicly supported reimposition of the 55 mph speed limit in a speech to the New York Press Club.

On July 3, 2008, U.S. Senator John Warner, R-VA, wrote a letter to Energy Secretary Samuel Bodman asking to look into what speed limit would provide optimum gasoline efficiency given current technology. He said he wants to know if the administration might support efforts in Congress to require a lower speed limit. In that same month, a Rasmussen poll of American voters found that 59 % oppose reducing the speed limits in the United States to 55 mph.

Definition of speeding

Either of the following qualifies a crash as speed-related per U.S. government rules:

1. Exceeding speed limits.
2. 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:

1. When speed limits are set through political rather than empirical processes, the speed limit's relationship to safe speeds is questionable or intentionally eliminated. Therefore, crashes that occur at speeds in excess of the limit can count as speed-related even when it is unclear whether the speed was unsafe.
2. Conditions exist where speed under the effective limit may still be too fast, 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.

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 offers motorists a valid defense to a speeding charge if it can be proven that the speed was in fact reasonable and prudent.

A successful prima facie defense is rare. Not only does the burden of proof rest upon the accused, a successful defense may involve expert witnesses or other expenses well in excess of the cost of a ticket. Furthermore, because prima facie defenses must be presented in a court, such a defense is difficult for out of town motorists. 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.

Jurisdictional distinctions

Alabama

In Alabama, trucks carrying hazardous materials are not to exceed 55 mph. A speed limit of 30 mph in urban areas and 35 mph on unpaved rural roads is enforced. The speed limit for rural paved roads is 45 mph. On the Interstate, it is 55 mph.

Alaska

Speed limits in Alaska are 15 mph in alleys, 20 mph in a business district, 25 mph in a residential district, and 55 mph on other roads.

Arizona

The default speed limit outside of "business or residential" districts in Arizona is 65 mph, within those districts the default speed limit is 25 mph. The school zone speed limit is 15 mph. 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 75 mph. This limit may be applied outside of "urbanized areas", where 85 mph on any highway is considered "excessive". Within "business or residential" districts, exceeding the speed limit by 20 mph is considered "excessive". Within "urbanized areas", 55 mph speed limit citations are given for "waste of a finite resource". This exception only applies within a 10 mph threshold. As long as the speed does not exceed 65 mph, the infraction is not recorded as a traffic violation for the purposes of a point system. Nonetheless, exceeding these 55 mph limits, effective on many freeways in Phoenix, for example, is illegal.

Non-passenger vehicles in excess of thirteen tons, or "vehicles drawing a pole trailer" weighing more than 3 tons may not exceed 65 mph 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 65 mph.

A non-numeric minimum speed limit is incorporated with the basic speed rule in Arizona, which also prohibits speeds that are less than "reasonable and prudent".

California

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 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 identified as "maximum speed", usually when the limit is 55 mph (89 km/h) or more. 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.As attorney David W. Brown says in his book Fight Your Ticket & Win in California, "a person traveling over the speed limit–but less than the usual 65 mph maximum speed (55 mph for two-lane undivided highways)–isn't necessarily violating the law" and that "you can defend against a charge of violating the Basic Speed Law not only by showing you weren't exceeding the speed limit, but also by establishing that even if you were over the limit, your speed was nevertheless 'safe' under the circumstances."

The speed limit on rural freeways, such as parts of I-5, I-8, I-10, I-15, I-40, and U.S. 101 on the central coast, and SR 99 south of Madera and Fresno, have 70 mph (113 km/h) speed limits. Because I-80 passes exclusively through urban and mountainous areas, its highest speed limit is only 65 mph. (Everyone knows people go 80 on 80. It's California.) In downtown Los Angeles, the maximum speed limit is 55 MPH. 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 2-lane roads is 55 mph. However, Caltrans or a local agency can post a speed of up to 65 mph after an engineering study.

All of these highways feature supplementary signage stating "AUTOS WITH TRAILERS/TRUCKS 55 MAXIMUM". Maximum truck/autos with trailers limit applies to trucks with 3 or more axles and all vehicles when towing. As of 2007, these signs are being replaced with signage stating "ALL VEHICLES WHILE TOWING 55 MAXIMUM".

In California, the Maximum Speed in school zones is 25 mph, but is in effect only if children are present within that school zone.

Connecticut

Speed limits are normally 65 MPH on rural freeways; up to 55 MPH on rural divided and undivided highways. In urban areas speed limits vary from 25 MPH on residential streets and central business districts to 30-40 MPH on arterial roadways, and from 45-55 MPH on urban freeways. Limited-access divided highways have a minimum speed of 40 mph (64 km/h), but this is not always posted.

Speed limits for all roads within Connecticut--including local streets--are established by the State Traffic Commission, an agency composed of members of the Department of Motor Vehicles (CTDMV), the Department of Public Safety, and the Department of Transportation (CONNDOT).

The State Traffic Commission typically sets speed limits following engineering studies performed by CONNDOT. Data used in setting speed limits includes (but not limited to): traffic volume vs. roadway capacity, design speed, road geometry, spacing of intersections and/or interchanges, number of driveways and curb cuts, and accident rates.

Municipalities are normally required to seek approval from the State Traffic Commission for changes to the posted speed limits on locally-owned streets after appropriate engeneering studies are performed.

Speeding fines are doubled in school zones and construction areas.

Prior to 1974, Connecticut permitted a maximum speed of 70 MPH on rural freeways.

Delaware

In Delaware, only two roads have a 65 mph (105 km/h) speed limit: I-495 and Delaware Route 1. Interstate 95 is 55 mph (89 km/h) and Interstate 295 is 50 mph (80 km/h).

All rural two-lane state-owned roads have 50 mph (80 km/h) speed limits, while all urban speed limits, regardless of location, are held at 25 mph (40 km/h) for two-lane roads and up to 35 mph (56 km/h) for four-lane roads. Four lane highways such as US 13 and US 113 are normally 55mph.

School zones have 20 mph (32 km/h).

Interstate 495, which forms a bypass around Wilmington, Delaware, features changeable speed limit signs for environmental purposes. These signs typically display a 65 mph speed limit, but this limit changes to 55 mph on days when air quality is a concern.

Florida

Florida raised its speed limit from the federally mandated 55 mph national limit (1974-1987) to 65 mph in 1987. In 1996, after the 1995 repeal of federal speed limit controls, Florida raised the speed limit to 70 mph on expressways, including rural Interstate Highways, and limited access toll roads; 65 mph on rural 4-lane highways (including US and State highways); and 60 mph on rural 2-lane highways.

Florida typically does not post night speed limits, but there are a few exceptions. For the most part, these night time reduced speeds are located in wildlife preserves for such endangered species as the Florida panther and the key deer. Most of the Tamiami Trail through the Big Cypress National Preserve has a 45 mph night speed limit. On some stretches of road where the speed limit is reduced at night, the daytime speed limit sign is not reflective so at night, only the night limit is visible.

County roads typically have 55 or 60 mph limits.

Florida's minimum speed limit on Interstate Highways is now 50 mph in most 70 mph zones, up from the previous 40 mph minimum. In 55 mph, and 65 mph urban interstate zones, the minimum remains 40 mph.

The State of Florida also does not impose a lower truck speed limit.

All interstate traffic is permitted to travel at the same speed.

School zones in Florida usually have 10 mph to 20 mph limits. Most have flashing yellow lights activated during the times they are in effect as well as accompanying signs which post the times these reduced speed limits are effective. All are strictly enforced and carry an increased penalty for violations.

Hawaii

Hawaii was the last state to raise its maximum speed limit after the National Maximum Speed Law was repealed in 1995. In 2002, after public outcry after a controversial experiment with speed enforcement using road safety cameras, the state Department of Transportation raised the speed limit to 60 mph on two stretches of road:

• Interstate H-1 between Kapolei and Waipahu, and
• Interstate H-3 between the Tetsuo Harano Tunnels and the junction with H-1.

All other freeways, including Interstate H-2, have a maximum speed limit of 55 mph, with the limit dropping to 45 mph in central Honolulu. Other highways generally have speed limits of 55 mph and in many cases much less.

Hawaii has a minimum speed along much of Interstate H-1 of only 10 mph below the speed limit. The minimum speed is usually 45 mph when the speed limit is 55, and 40 mph when the speed limit is 50.

Illinois

Interstate Highways are usually posted with both minimum and maximum speed limits, except in some urban areas, particularly Chicago. Most expressways surrounding the Chicagoland area, in Cook, DuPage, Lake, and Will Counties maintain a 55mph speed limit. No expressway in Cook county exceeds a speed limit of 55mph due to the high-population density. In downtown Chicago, where all the major expressways merge together, the speed limit is reduced to 45mph due to high-traffic density and frequent entering/exiting of the expressways. All other expressway areas in Illinois maintain a 65mph speed limit, except in areas approaching a major city where the speed limit may be reduced to 50 or 55. A construction zone almost always has a light posted to the speed limit sign that, when flashing, indicates to the driver that the construction speed limit must be obeyed. When the light is not flashing, drivers may obey the regular speed limit.

Indiana

In Indiana speed limits on Interstate Highways are usually 70 mph (113 km/h) for cars and 65 mph (105 km/h) for trucks with a gross vehicular weight (GVW) of 13 tons or greater, except in urban areas, where it is generally 55 mph (89 km/h) in city centers and 65 mph (105 km/h) cars/60 mph (95 km/h) trucks in suburban areas. Prior to July 5, 2005, all Interstate Highways were 65 mph and below.

Most non-Interstate Highways are 55 mph, but some rural four-lane divided highways are set at 60 mph. These limits often decrease to 30-45 mph (48-72 km/h) approaching urban areas, and within cities a speed limit of 20–30 mph (32–48 km/h) is not uncommon, though larger arterial roads within cities may reach as high as 45 mph (72 km/h).

Iowa

Iowa's rural Interstate's speed limits are typically 70 mph (113 km/h), with no distinction made for trucks. Urban Interstate speed limits are usually set at 65 mph (105 km/h), with 55 mph speed limits set within cities, such as Interstate 235 in Des Moines. The Iowa DOT just recently increased the suburban speed limit on Interstate 235 to 60 mph, with 55 mph still effective for the downtown Des Moines area; 60 mph speed limits also exist on IA 58 and US 218 in Cedar Falls/Waterloo and on Interstate 380 outside of downtown Cedar Rapids.

Non-Interstate divided highways are signed at 65 mph with speeds dropping to 55 mph in urban areas. Two lane rural state and county highways have a 55 mph speed limit.

Rural Interstates have a minimum speed limit of 40 mph, and U.S. Highway 20 between Interstate 35 and Dubuque also has a 40 mph minimum speed, alongside a 65 mph maximum. Other four-lane divided rural highways are signed at 65 mph, with no minimum speed (with the purpose of allowing slow-moving farm vehicles to use the road as well).

Kentucky

In July 2007, Kentucky raised its rural freeway speed limits from 65 to 70 mph. Kentucky does still have limits of 55 in some urban areas (I-71/75 near Cincinnati, I-64 and Interstate 264 in Louisville) with one 50 MPH area approaching the Sherman Minton Bridge crossing the Ohio River into Indiana on I-64.

Louisiana

In August 2003, Governor Mike Foster announced speed and lane restrictions on trucks on the 18 mile (29 km) stretch of Interstate 10 known as the Atchafalaya Swamp Freeway. The restrictions lower the truck speed limit to 55 mph and restrict them to the right lane for the entire length of the elevated freeway.

Michigan

Freeways in Michigan are usually signed with both minimum and maximum speeds. Typically the freeway speed limit is 75 mph. The minimum speed is usually 45 to 55 mph for all vehicles, despite a maximum speed limit of 60 mph for trucks — effectively permitting trucks only a 5 mph range of legal speeds.

Minnesota

A 70 mph speed limit is only allowed on Minnesota's rural freeways. A speed limit of 55 mph is typically used in urban areas where a higher speed limit might be used, but traffic congestion or other reasons require a lower speed limit. Examples include I-94, I-35W and I-35E in and around Minneapolis and Saint Paul. A speed limit of 60 mph is typically used in suburban areas such as I-494 and I-694 loops in the Twin cities metro area.

Non-Interstate divided highways (both freeways and rural expressways) such as sections of US-169 and US-212 have speed limits of 65 mph in rural areas and 55 or 60 mph in urban or suburban areas. Undivided sections have speed limits of 55 or 60 mph. Two lane county roads also have speed limits of 55 or 60 mph.

Mississippi

A speed limit of 70 mph is only allowed on Mississippi's rural freeways; only the Interstates (except I-110), U.S. Highway 78, Mississippi Highway 304, and a portion of U.S. Highway 82 have speed limits of 70 mph.

A speed limit of 65 mph is typically used on the state's four-lane divided highways, which include the following roadway segments:

• US 45 and US 45 Alternate
• US 49 from Gulfport to Florence and from Jackson to Yazoo City
• US 49W from Yazoo City to Indianola
• US 61 from Woodville to Tunica EXCEPT for the portion near Alcorn State University which has not been upgraded to four-lane.
• US 82 from Greenville to Starkville
• US 84 from Natchez to Waynesboro
• US 72 east of MS 302
• US 98 east of McComb
• US 90 west of Waveland and east of Ocean Springs
• US 278 / MS 6 from Batesville to east of Pontotoc
• MS 15 just north of Louisville
• MS 18 from Raymond to Jackson
• MS 19 from Meridian to Collinsville
• MS 25 from Brandon to Starkville and just north of Fulton
• MS 39 from Meridian to Meridian Naval Air Station
• MS 63 from Escatawpa to Lucedale
• MS 302 east of Olive Branch
• MS 67
• MS 607 south of the John C. Stennis Space Center

A speed limit of 60 mph is typically used in urban areas where a higher speed limit might be used, but traffic or geometric conditions constitute a lower speed limit. Examples include the following roadway sections:

• I-20 in Vicksburg, Jackson, and Meridian
• I-55 in Jackson, I-59 in Laurel (the speed limit drops to 40 mph, due to a dangerous "S-curve") and Meridian
• U.S. Highway 49 in Gulfport
• U.S. Highway 61 at Tunica Resorts
• US 78 in New Albany
• U.S. Highway 82 in Columbus.

House Bill 3, passed during the 2008 First Extraordinary Session of the state legislature, permits speed limits up to 80 mph (130 km/h) on toll roads in the state; however, as of 2008, no such road has been constructed.

Mississippi has a minimum speed of 30 mph on four-lane U.S. highways when no hazard exists. Strangely, there is no law for the minimum speed of the state's growing number of four-lane state highways. The minimum is 40 mph on Interstate Highways and on four-lane U.S. designated highways which have a 70 mph speed limit. In 2004, Mississippi posted minimum speed limits (40 mph) on all rural Interstates, but this minimum speed limit was already state law before then.

Missouri

Missouri recently began a two-year experiment with variable speed limits along Interstate 270 around St. Louis. Digital signs have been erected along the highway as well as additional signs alerting drivers about the use of variable speed limits. The limits will vary between 40 and 60 miles per hour, depending on traffic conditions, and could change by up to 5 mph every 5 minutes.

Interstate Highways have minimum speed limits of 40 mph.

Montana

Reasonable and prudent

In the years before 1974's national 55 mph limit, and for three years after the 1995 repeal of the increased 65 mph limit, Montana had a non-numeric "reasonable and prudent" speed limit during the daytime on most rural roads. Montana Code Annotated (MCA) Section 61-8-303 said "A person . . . shall drive the vehicle . . . at a rate of speed no greater than is reasonable and proper under the conditions existing at the point of operation . . . so as not to unduly or unreasonably endanger the life, limb, property, or other rights of a person entitled to the use of the street or highway."

Typical speed limit sign that one would see at the Montana state line from December 1995 to June 1999.

Montana law also specified a few numeric limits: a night speed limit, usually 55 or 65 mph (89–105 km/h), depending on road type; 25 mph (40 km/h) in urban districts and 35 mph (56 km/h) in construction zones.

The phrase "reasonable and prudent" is found in the language of most state speed laws. This allows prosecution under non-ideal conditions such as rain or snow when the speed limit would be imprudently fast.

No speed limit

On March 10, 1996, a Montana patrolman issued a speeding ticket to a driver traveling at 90 mph (145 km/h) on a stretch of State Highway 200. The 50 year-old driver was operating a 1996 Camaro with fewer than 10,000 miles (16,000 km) on the odometer. Although the officer gave no opinion as to what would have been a reasonable speed, the driver was convicted. The driver appealed to the Montana Supreme Court. The Court reversed the conviction in case No. 97-486 on December 23, 1998; it held that a law requiring drivers to drive at a non-numerical "reasonable and proper" speed "is so vague that it violates the Due Process Clause ... of the Montana Constitution".

Effective May 28, 1999, as a result of that decision, the Montana Legislature established a speed limit of 75 mph.

75 mph speed limit

Despite this reversal, Montana's then Governor, Marc Racicot, did not convene an emergency session of the legislature. Montana technically had no speed limit whatsoever until June 1999, after the Montana legislature met in regular session and enacted a new law. The law's practical effect was to require numeric speed limits on all roads and disallow any speed limit higher than 75 mph (121 km/h).

Montana law still contains a section that says "a person shall operate a vehicle in a careful and prudent manner and at a reduced rate of speed no greater than is reasonable and prudent under the conditions existing at the point of operation, taking into account the amount and character of traffic, visibility, weather, and roadway conditions." However, this is a standard clause that appears in other state traffic codes and has the practical effect of requiring a speed lower than the speed limit where a lower speed is necessary to maintain a reasonable and prudent road manner.

Montana also has limited sections of night speed limits.

New Hampshire

The highest speed limit in New Hampshire is 65 mph (105 km/h). It can be found on Interstate Highways, the Everett Turnpike, and the New Hampshire Turnpike.

Provided that no hazard exists that requires lower speed, the speed of any vehicle not in excess of the limit is deemed to be prima facie lawful. The limit for "rural residential districts" and Class V highways outside the city or town compact is 35 mph. The limit for any "business or urban residence district" is 30 mph. School zones receive a 10 mph reduction in the limit 45 minutes before and after the beginning and end of a school day. The speed limit for a road work or construction area is 10 mph lower than the normal speed limit, but not more than 45 mph, when work is in progress. The speed limit for all other locations is 55 mph. The minimum limit that a speed can be set in a rural or urban district is 25 mph.

New Jersey

The common speed limit on a divided highway in New Jersey is 65 mph. Highways such as the New Jersey Turnpike (which uses variable electronic speed limit signs near Newark, New Jersey|Newark) south of Exit 12, the Atlantic City Expressway (north of the Garden State Parkway), the Garden State Parkway (north of Exit 163 in Paramus and south of the Sayreville toll barrier), New Jersey Route 55, I-80, I-287, and I-78 have 65 mph limits where speeding fines are doubled. Residential roads have 25 mph speed limits. Two-lane rural highways and two-lane county roads generally have 45 and 50 mph limits.

New Mexico

With the exception of wartime, New Mexico had no default numeric speed limit until the early 1950s. Prior to the national 55 mph limit in 1974, the speed limit on rural Interstates was 75 miles per hour during the day and 70 mph at night. Primary highways in open areas had daytime speed limits of 70 mph and nighttime ones of 60 mph. Secondary highways in open areas had daytime speed limits of 60 mph and nighttime ones of 50 mph. Before the end of federal speed controls, the maximum speed limit was 65 mph on Interstate routes and 55 mph elsewhere. In May 1996 legislation enacted by Governor Gary E. Johnson raised the absolute speed limit in New Mexico to 75 mph. Signs are posted on the vast majority of the mileage of Interstate routes to that effect.

New Mexico has six major freeway facilities which include three lengthy Interstate routes. Part of US-70 (as both a freeway and then a divided highway) between Las Cruces and Alamogordo is the only section of non-Interstate route to have the 75 mph limit. There is no statutory requirement for reduced speeds on urban freeways so that, for example at Santa Fe and Las Vegas the speed limit remains 75 mph on I-25. Nonetheless, there are 65 mph limits on freeways in more heavily urbanized areas such as Albuquerque and Las Cruces. Other reduced speed limits do exist, but the lowest speed limit under normal conditions on New Mexico's freeways is 55 mph.

By statute, Other state maintained roads may have speed limits of up to 75 mph. [87] Four lane divided highways in open areas often have 65mph limits, with some 70mph limits, such as almost the entire length of US 550 from Bloomfield to Bernalillo. There is a trend toward posting a 70mph limit on these highways, such as the recent 70mph speed limit posting (increased from 65mph) on a 23 mile stretch of U.S. 70 west of Roswell.

Primary 2 lane highways in open areas with parking shoulders often have 65mph limits.

Most primary 2 lane highways without parking shoulders in open and mixed rural areas still have a 55mph limit, but some have 60mph limits.

A 65 mph left lane minimum speed limit is sometimes indicated on 75 mph roads with steep grades, "slower traffic keep right" is also in effect. On one-way roadways state law reserves the left and center lanes of two or more lanes for passing. There are reduced advisory speed limits for some roads during poor weather. Speeding fines are doubled in construction zones and designated safety corridors, with signs often stating this. There are no longer night speed limits, nor are there any differential speed limits for heavy trucks.

There are two other statutory speed limits in New Mexico which are often altered, especially on urban arterials or even city or countywide: thirty miles per hour in a "business or residence district" and fifteen miles per hour near schools at certain times. For example, in Albuquerque the default speed limit is thirty miles per hour as per state law, but many streets have a different speed limit. Some school zones there have twenty mile per hour speed limits. The city of Santa Fe's default speed limit is twenty five miles per hour. Although there are no signs to make drivers aware of the altered limit, the limit is signed on most roads where it applies. The county of Los Alamos alters the urban default and absolute speed limits to twenty five miles per hour and 50 mph respectively, but posts signs at county lines.

New York

A standard-style New York State speed sign indicating the 'State Speed Limit'.

The highest speed limit in New York is 65 mph (105 km/h), which is found on most of the New York State Thruway and other rural Interstate Highways. The State Speed Limit (a blanket or default speed limit for rural roads) is 55 mph (89 km/h), which is also the highest a non-expressway or parkway highway may have. Many 55 mph signs in New York thus read "State Speed Limit". The theme is followed, and many signs read "Area Speed Limit", "Town Speed Limit", "City Speed Limit" or "Village Speed Limit" with varying speeds shown below. In New York State, the default speed limit on any road not marked with a speed limit sign is 55 mph (unless local restrictions are stricter). New York City and some other urbanized areas have a default speed limit of 30 mph (48 km/h) except where otherwise posted. The highest speed limit on expressways and parkways in New York City is 50 mph (80 km/h), with many freeways having a lower speed limit (such as the FDR Drive with its 40 mph limit) that may vary based on a section of road (Like Sections of the Brooklyn-Queens Expressway, having only a 35 mph speed limit).

Governor George Pataki signed legislation in September 2003 that enables NYSDOT and NYSTA to raise speed limits to 65 mph on its roads that meet established design and safety standards. This legislation became active in March 2004, and has been used on over 100 miles worth of highway. An example of this is a 3-mile section of NY Route 7 (locally known as "Alternate Route 7") which connects Exit 7 of Interstate 87 (the Adirondack Northway) with Interstate 787, the main highway into the city of Albany. Prior to the new law, consent of the state legislature was necessary to enact a 65 mph speed limit, a process that could take months or years. In fact, New York was one of the last states in the United States to enable speed limits above 55 mph on any roads.

A minimum speed limit of 40 mph has been set on the entire length of Interstate 787 and the entire length of The Long Island Expressway. The New York State Thruway does not have a firm minimum speed, but there are signs advising drivers to use their flashers when traveling at speeds below 40 mph.

While New York does not have truck speed restrictions per se, the New England Thruway (Interstate 95) features "State Speed Limit 55" signs right next to "Truck Speed Limit 50" signs.

North Carolina

Along two lane rural primary and secondary roads outside municipal limits, the statutory speed limit is 55mph unless otherwise posted. Inside the municipal limits, the statutory speed limit is 35mph unless otherwise posted. The downtown statutory speed limit is 20mph unless otherwise posted. "Reduced Speed Ahead" signage is the norm whenever the speed limit drops at any level. Three to eight lane boulevards with or without center turn lanes, range from 35mph to 50mph within municipal limits statewide.

School zone speed limits are generally entail a 10 to 20 mph reduction below the original speed limit during open school hours of arrivals and departures. Such a speed limit would be indicated when entering the school zone. Also, the default or modified speed limit is indicated after leaving the school zone. A school zone speed limit cannot be less than 20mph.

Military bases are generally posted at the maximum of 50mph. The exceptions are any primary or state secondary numbered highways such as N.C. Highway 690 along the north side of Fort Bragg, Bragg Boulevard (also known as N.C. Highway 24) and the All American Freeway.

The state park speed limit is 25mph unless otherwise posted. These are not limited to places like Hanging Rock State Park and Mount Mitchell State Park.

The Blue Ridge Parkway is 45mph. However, there are occasional 35mph stretches. The National Park Service is responsible for highway maintenance and speed enforcement.

The county governments of North Carolina do not have any control over speed limits except municipalities. The exception of this rule are city-county governments like Charlotte.

Freeways and expressways with no primary route number are under the state secondary road system where it's route number is 1000 or above. They are posted at the maximum of 55mph.

60mph speed limits are growing in popularity into replacing 55mph boulevard and expressway segments throughout the state. The boulevard speed limit changes go against the NCDOT rationale behind signing 60mph speed limits along only freeway and expressway segments. As of June 1, 2008, some examples of the affected boulevards are US 17 north of Elizabeth City, US 74 east of Wadesboro and NC 11 in Pitt County. Some examples of the affected expressways are US 1 in northeastern Moore County, US 17 on bypass routes in Brunswick County, US 74 east of I-95, US 117 in Wayne County and US 220 in Rockingham County.

There is a default minimum speed limit on Interstate and primary highways only when signs are present. The minimum is 40 mph if the maximum is 55 mph. The minimum is 45 mph if the maximum is at least 60 mph. These minimums do not apply to vehicles that are towing other vehicles.

North Dakota

The highest speed limit found in North Dakota is 75 mph, which can be found on Interstates 29 and 94. Rural four-lane divided highways are 70 mph. Rural 2-Lane Federally numbered, and State Highways have 65 mph limits. Four-lane divided, Federally numbered, and State Highways that pass through cities have 25-65 mph limits. 65 mph speed limits on county roads can be found on portions in Ward County (CR 23) and Burleigh County (CR 10). Certain major county roads have 50-55 mph statutory limits for cars and 30-45 mph for trucks. A default 55 mph speed limit applies on other county roads. Speed limits on surface streets range from 30-40 mph. Residential streets are generally 15-25 mph. School zones are 15-25 mph.

Ohio

The maximum speed limit found on highways in Ohio is 65 miles per hour.

Historically, Ohio had speed limits of 70 miles per hour (110 km/h) prior to 1974.

In Cuyahoga County, the maximum speed limit is 60 mph. This speed limit was lowered for safety concerns brought to the Ohio State Legislation from Cleveland and its suburbs. The only interstate in Cuyahoga County above 60 mph is I-80, the Ohio Turnpike.

A minimum speed of 45 mph is on Interstate 70 in downtown Columbus, where the maximum limit is 55 mph. US-35 in Dayton has a minimum speed limit of 40 mph with a maximum of 55 mph. There also sections of freeway in Toledo with 60 mph speed limits.

Ohio Governor Ted Strickland signed House Bill 2 into law on April 1st, 2009 at 11:30 p.m. EDT, that now allows truckers to travel at a speed of up to 65 mph on interstate highways. This is an increase from a previous limit of 55 mph for trucks except on the Ohio turnpike where the truck speed limit has been 65mph. The law officially goes into effect on July 1, 2009. . Technically this law became effective upon being signed because the bill was passed as an emergency, but the signage will need to be changed on the affected highways.

A bill has been introduced in the State senate that would increase rural freeway speed limits to 70 mph.

Oklahoma

In Oklahoma, the maximum speed limit is 75 miles per hour on turnpikes and 70 mph on all other freeways. Most other rural highways have a 65 mph speed limit (although some rural divided highways have a 70 mph limit). Minimum speed limits that are 25 mph below the maximum speed limit on more or less all Interstate Highways. For example, on the turnpikes, which have a maximum speed limit of 75 mph, they are nearly always accompanied by a sign stating a minimum speed limit of 50 mph.

Where turnpikes are signed with a speed limit of 75 miles per hour, a sign warning "no tolerance" is posted, warning drivers state troopers will write tickets for speeding for ANY violation of this higher limit.

Oregon

A standard-style Oregon speed sign removing the word "limit".

Up until 2002, Oregon state law required that all speed limit signs remove the word limit from their display. The reasoning behind this is unknown but the practice has been known to produce some unusual number fonts. The spacing between and appearance of the numbers on the signs vary greatly depending on which jurisdiction made the sign. In 2002, the Oregon Department of Transportation permitted the inclusion of the word "limit" on speed signs and left it up to local government agencies to decide on whether "limit"-branded signs would be installed. Most have chosen not to change over with a few exceptions to the rule. Speed Limit 60 signs can be found on Interstate 5 through Salem and on Interstate 84 through east Portland. The City of Beaverton has been the most liberal in retrofitting the standard-form Speed Limit sign, presumably because the "SPEED" signs do not use a standard number font and are likely more expensive to make. Whenever a "Speed" sign is damaged or vandalized in Beaverton city limits, a "Speed Limit" sign takes its place.

Throughout the late 1990s the Oregon state legislature passed multiple bills that would have raised the speed limit to 75 miles per hour on rural Interstate Highways and up to 70 mph on certain rural two lane highways in the eastern portions of the state. Each year Governor John Kitzhaber vetoed the bill. In 2003, the Oregon state legislature passed a bill that would have raised the maximum permissible speed limit on Interstate Highways to 70 mph for cars with a 5 mph differential for trucks, up from the previous 65 mph limit for cars with a 10 mph differential, this bill was signed into law by then newly elected Governor Ted Kulongoski. In 2004 the Oregon Department of Transportation decided to not implement the increase out of concerns that it would not be safe to have trucks traveling at 65 mph. Prior to the National Maximum Speed Law, the speed limit on Oregon interstates could be as high as 75 mph. Oregon remains the only state west of the Mississippi River to have a maximum state speed limit that is under 70 mph.

In 2004, a law was passed revising Oregon's school speed limit laws. In school zones, on roads with speed limits of 30 mph or below, drivers were required to slow to 20 mph 24 hours a day, 365 days a year, regardless of whether or not children were present. This replaced most 'when children are present' placards. If the speed limit was 35 mph or higher, the school zone limit would be imposed either by flashing yellow lights or a placard denoting times and days of the week when the limit was in effect. The at-all-times rule was highly unpopular with motorists and was widely ignored. In fact, it is likely that this law has led to a reduced acceptance of school speed limits, regardless of how and when they are in effect. In 2006, the law was revised again, taking away the 'at all times' requirement and replacing it with a time-of-day system (usually school days, 7 a.m. to 5 p.m.). School crossings with flashing yellow lights remain.

Pennsylvania

In 1940, when the Pennsylvania Turnpike was opened between Irwin and Carlisle, the entire 110 mile limited-access toll road did not have a speed limit, similar to that of the German Autobahns. In 1941, a speed limit of 70 mph (113 km/h) was established, only to be reduced to 35 mph (56 km/h) during the war years (1942–45). After WWII, the limit was raised to 70 mph on the four-lane sections, with the two-lane tunnels having 50 mph (80 km/h) for cars and 40 mph (64 km/h) for trucks. Prior to the 1974 federal speed limit law, all Interstates and the Turnpike had a 65 mph (105 km/h) speed limit on rural stretches and 60 mph (97 km/h) speed limit in urban areas.

In 1995, the state raised the speed limit on rural stretches of Interstate Highways and the Pennsylvania Turnpike system to 65 mph (105 km/h), with urban area having a 55 mph (89 km/h) limit. In 1997, PennDOT raised the speed limit to some rural non-Interstate Highway bypasses to 65 mph (105 km/h). In 2005, with the change in the designation of "urban zones" in the state, the entire lengths of both the Pennsylvania Turnpike's east-west mainline and Northeast Extension were given 65 mph (105 km/h) limits, except at the tunnels and through the very winding 5.5 mile (9 km) eastern approach to the Allegheny Mountain Tunnel.

On non-freeway roads, speed limits are generally held at 65 mph (105 km/h) for rural four-lane roads, 55 mph (89 km/h) for rural two-lane roads, 45-55 mph (89 km/h) for urban four lane roads and 40-45  mph (64 km/h) for urban two lane roads, 35-45 mph for roads in commercial business areas, 35 mph (56 km/h) for major roads in residential areas, 25 mph (40 km/h) for most municipal residential streets, including main north–south and east–west roads in county seats, and 15 mph (25 km/h) for school zones during school arrival and departure times only. It is also only in effect on days that the school the road goes near is in session. Many schools have signs that blink when the school speed limit is in effect. There is no reduced school speed on divided highways, even if the school sits right beside the highway.

Pennsylvania has a minimum speed limit of 15 mph below the speed limit. Therefore, the minimum speed is 50 mph when the speed limit is 65 mph, and 40 mph when the speed limit is 55 mph. Motorists are require to use flashers when traveling 15 mph below the speed limit on any road in Pennsylvania. The Pennsylvania Turnpike Commission states that vehicles that cannot maintain this speed on a level road may not use the turnpike. This minimum speed is not generally signed.

Puerto Rico

The US territory of Puerto Rico regulates and posts speed limits in miles per hour, although highway signage for distances are in kilometers. Tolled Autopistas can have speed limits up to 65 mph, while other expressways have speed limits up to 60 mph. The maximum statutory speed limit for any expressway may in theory be 65 mph. The rural default speed limit is 45 mph but may be increased to 55 mph. In residential areas, only multilane roads have limits up to 35 mph, other roads are restricted to a maximum speed of 25 mph. Only rural school zones have the higher 25 mph limit. Speed limits for "heavy motor vehicles", such as school buses, are always 10 mph lower than that allowed for lighter vehicles, except in urban school zones where the limit is 15 mph. Vehicles carrying hazardous materials are limited to 30 mph in rural areas and 15 mph in urban ones.

South Dakota

Shortly after the December 1995 repeal of the 65/55 mph National Maximum Speed Law, South Dakota raised its general rural speed limits to 75 mph on freeways and 65 mph on other roads. Almost a decade after posting the 75 mph limit, average speeds on South Dakotan rural freeways remain at or below the speed limit. South Dakota also has the distinction of being the only state that does not assign points to one's driving record for speeding convictions.

Texas

Typical Texas rural speed limit sign. Note the black backgrounded 65 mph night speed limit sign, common on Texas roads. (No other state has a universal night speed limit.) This sign is on southbound U.S. 69/96/287 just north of Beaumont.

Texas is the only state that does not prescribe a speed limit for each road type. Any rural road—two lane, four lane, freeway, or otherwise—that is numbered by the state or federal government (United States Numbered Highways and Interstate Highways) has a 70 mph (113 km/h) statutory limit. The law generally allows changing the 70 mph limit only if a study recommends a different limit.Unlike other Texas county roads, which have 60 mph maximum speed limits, Harris County's toll road authority may post up to 70 mph limits on its tollway system.

I-10 within the El Paso city limits has a minimum speed limit of 45 mph.

Night speed limits

Texas statutorily prescribes a 65 mph (105 km/h) night speed limit on all roads. In practice, roads with a daytime limit below 65 mph retain that lower limit at night. While the Texas Transportation Commission has the power to raise the night speed limit to 70 mph, it has never done so. Virtually all 70 mph or higher speed limit signs have an accompanying 65 mph night speed limit sign. Two exceptions:

1. a 55 mph night speed limit for trucks on farm to market roads, complementing the statutory 60 mph truck day limit on these roads. (This is a holdover from Texas's truck speed limits.)
2. a 55 mph night speed limit on county roads (except for Harris County Toll Road Authority-owned toll freeways).

Environmental speed limits

55 mph speed limit signs photographed on August 20 2002. These signs were on southbound I-45 at the north border of Montgomery County. Immediately before this point, the speed limit was 70 mph. These were part of an unpopular 55 mph speed limit cap in the Houston–Galveston area.

Same location as prior picture with the more recent 65 mph speed limit, photographed on August 4 2005.

Texas is the first state to lower speed limits for air quality reasons. In roughly a 50 mile (80 km) radius of the Houston–Galveston and Dallas–Ft. Worth regions, the Texas Commission on Environmental Quality convinced the Texas Department of Transportation to reduce the speed limit on all roads with 70 mph (113 km/h) or 65 mph (105 km/h) speed limits by 5 mph. This was instituted as part of a plan to reduce smog-forming emissions in areas out of compliance with the federal Clean Air Act.

Initial studies found that lower speed limits could bring the areas roughly 1.5% closer to compliance. However, follow up studies found that the actual reduction is far less:

1. The emissions modeling software initially used, MOBILE 5a, overestimated the emissions contribution of speed limit reductions. Rerunning the models with the next generation software, MOBILE 6, produced dramatically lower emissions reductions.
2. Speed checks in the Dallas area performed 1 year after implementation of speed limit reductions show that actual speed reductions are only about 1.6 mph, a fraction of the anticipated 10% (5.5 mph) speed reduction.

With both of these facts combined, it is possible that the speed limit reductions only provide a thousandth of the total emissions reductions necessary for Clean Air Act compliance.

In mid-2002, all speed limits in the Houston–Galveston area were capped at 55 mph (89 km/h). Facing immense opposition, poor compliance, and the finding that lowered speed limits produced only a fraction of the originally estimated emissions reductions, the TCEQ relented and reverted to the 5 mph reduction scheme.

In 2003, the Texas Legislature prospectively banned environmental speed limits effective September 1, 2003. The wording of the bill allows environmental speed limits already in place to remain indefinitely; no new miles of roadway may be subjected to environmental speed limits, however.

This law has allowed interesting inconsistencies. Generally, all primary arterial roads within the inner loops of Texas cities have speed limits of 60 mph (95 km/h) or lower, so they were not subjected to environmental speed limits. Arterial roads between the inner loop and the outer loop generally have 65 mph (105 km/h) limits, and arterial roads outside the outer loop generally have 70 mph (113 km/h) limits. (Note that this is only the typical pattern and is not prescribed by law.) In at least one case—TX 121 between I-35W and I-820 in Ft. Worth—the speed limit rises from 60 mph to 65 mph as one crosses I-820 approaching downtown, contravening the standard.

Truck speed limits

File:IMG 3389 80mph i20 9 mi w of pecos 2007-01-11.jpg

Example of 70 mph truck speed limit sign immediately behind an 80 mph speed limit sign.

Texas formerly had a 60 mph (97 km/h) day/55 mph (89 km/h) night truck speed limit. This speed limit did not apply to buses or to trucks transporting United States Postal Service mail.

Whenever the speed limit on a road was above this threshold, separate truck speed limit signs were posted. These signs disappeared when all speed limits were capped at 55 mph (89 km/h) in 1974, but reappeared with the introduction of 65 mph (105 km/h) limits in 1987. Effective September 1, 1999, Texas repealed truck speed limits on all roads except farm to market and ranch to market roads.

Even after Texas repealed the truck speed limit, the Harris County Toll Road Authority erroneously retained the separate truck speed limits on its tolled freeways. The separate truck speed limits were removed with the 2002 adoption of the 55 mph environmental speed limit. The signs did not reappear when a 65 mph limit was imposed, but the truck speed limit sign posts are still standing as of August 2008.

2001 and 2003 statutes allowing 75 and 80 mph speed limits in certain areas of west and south Texas only apply to passenger vehicles. Truck speed limits remain 70 mph, so separate truck speed limit signs are slowly reappearing on these roads.

Due to the enormous unpopularity of a 55 mph speed limit cap that was imposed on the greater Houston area in 2002, the Texas Commission on Environmental Quality examined alternatives. Analysis suggested that the vast majority of emissions reductions from a 55 mph limit was from reduced heavy truck emissions. A proposed alternative was to restore passenger vehicle limits but retain a 55 mph truck speed limit. Concerns about safety problems and enforceability of such a large differential (up to 15 mph on many roads) scuttled that proposal, and a compromise plan, described above, was enacted that retained uniform, but still reduced, speed limits.

75 mph and 80 mph limits

Texas statutorily allows the Texas Department of Transportation to post 75 mph (121 km/h) speed limits in counties with average populations of fewer than 15 people per square mile. The same statute also allows 80 mph (129 km/h) speed limits on I-10 and I-20 in certain counties named in the statute, all of which happen to be rural, in west Texas, and have a low population density. Daytime truck limits are capped at 70 mph, and nighttime speed limits remain 65 mph for all vehicles. (Nothing prohibits nighttime speed limits from being raised to 70 mph, but the Department has not elected to do so.)

In 2001, the Texas Legislature allowed the Texas Department of Transportation to post 75 mph (121 km/h) speed limits in counties with fewer than 10 people per square mile. This had the practical effect of only allowing 75 mph speed limits in the most sparsely populated counties, all of which are generally well west of a line stretching from San Antonio to Odessa. In 2005, the Texas Legislature revised this law, allowing 80 mph (129 km/h) limits on I-10 and I-20 in certain rural counties in west Texas. This bill also revised the eligibility for 75 mph speed limits: now eligible counties can have up to 15 persons per square mile. This did not substantially increase the miles of roadway eligible for higher limits, however. A complete list of counties in which TxDOT may increase speed limits above 70 mph is found in the TxDOT Manual on Procedures for Establishing Speed Zones.

Texas Legislator Pete Gallego unveiling a new 80 mph speed limit sign on Interstate 10 near Fort Stockton, Texas.

On May 25, 2006, the Texas Transportation Commission has approved 80 mph speed limits, and signs are posted.

In a widely printed Associated Press story about the 80 mph speed limit, Texas is incorrectly reported as having legalized 75 mph limits in 1999. In fact, the bill that would have done this, HB 3328 by Pete Gallego, died in conference committee just before the Texas Legislature's session ended. This bill would have, in effect, set 75 mph as the statutory speed limit on any rural road numbered by the state or federal government, and it would have enacted—not simply allowed—an 80 mph speed limit on I-10 and I-20 in any county with fewer than 25,000 residents.

While Texas's 80 mph limit is higher than any limit authorized by another state except Utah, it is approximately one kilometer per hour less than the 130 km/h recommended speed on the Autobahn and the actual 130 km/h rural expressway speed limit in thirteen other European countries.

Because Texas law allows 75 mph speed limits on any road numbered by the state or federal government, it is the only state with 75 mph limits on two-lane roads. Several west Texas two-lane roads carry 75 mph limits, including portions of US 90. No other state has a limit higher than 70 mph on any two-lane road.

85 mph limits

The legislation creating the Trans-Texas Corridor allows speed limits of up to 85 mph (137 km/h) on roads built under the program. However, no such roads have been built as of April 2009. The language of the statute does not prohibit the Texas Transportation Commission from raising the truck speed limit or the night speed limit on these roads.

US Virgin Islands

For "motorcars, pick-up trucks, or motorcycles", the fastest speed limit in this territory is 55 mph and is found on one road, the divided Melvin H. Evans Highway on the island of St. Croix. Outside of towns, these vehicles are limited to 35 mph unless posted lower, except on the above mentioned divided highway and parts of Centerline Road, which is limited to 40 mph. Within towns, these vehicles are limited to twenty miles per hour.

"Motor trucks and busses" are limited to 40 mph on St. Croix's main divided highway, 30 mph on other highways outside of towns, and ten miles per hour within towns.

Utah

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80 Mile Per Hour speed limit sign on Interstate 15 south of Nephi, Utah.

In Utah, there is a minimum speed limit of 45 mph on Interstate Highways when conditions permit. The maximum speed limit on Interstates is 65 mph in cities and, on most highways, 75 mph elsewhere. In January 2009, the speed limit on two sections of I-15 together totaling 34 miles was raised to 80 mph as a "test."

Virginia

A Virginia statute provides that the default speed limit shall be 55 mph on Interstate highways, "other limited access highways with divided roadways," non-limited access highways with four or more lanes, and all state primary highways. "The maximum speed limit on all other highways shall be 55 miles per hour if the vehicle is a passenger motor vehicle, bus, pickup or panel truck, or a motorcycle, but 45 miles per hour on such highways if the vehicle is a truck, tractor truck, or combination of vehicles designed to transport property, or is a motor vehicle being used to tow a vehicle designed for self-propulsion, or a house trailer." The same statute contains a number of exceptions, however, allowing higher speed limits "where indicated by lawfully placed signs, erected subsequent to a traffic engineering study and analysis of available and appropriate accident and law-enforcement data." This provision allows speed limits of up to 65 mph on Interstate highways; multilane, divided, limited-access highways; and high-occupancy vehicle lanes if said lanes are physically separated from the regular travel lanes. (As of February 2009, Virginia has two such barrier-separated HOV facilities, one on I-95 and I-395 and the other on I-64.) The statute further authorizes a 70-mph speed limit on I-85, again "where indicated by lawfully placed signs, erected subsequent to a traffic engineering study and analysis of available and appropriate accident and law-enforcement data." Finally, the statute allows 60-mph speed limits on a number of specified non-limited access, multilane, divided highways.

Other Virginia statutes prescribe exceptions to the general rules set forth above. The notable aspect of Virginia's current speed limit laws is that the Department of Transportation has no authority to raise speed limits above the prevailing 55- and 65-mph limits unless the General Assembly passes a statute permitting the change. Since the National Maximum Speed Law was repealed in 1995, such statutory exceptions have largely been confined to a highway-by-highway basis, as evidenced by the list of exceptions in Va. Code § 46.2-870. While the statute authorizes 65-mph limits on all Interstate highways in Virginia after traffic engineering studies and law-enforcement data are examined, in practice Virginia generally retains the "55-mph urban/65-mph rural" system prescribed by the old National Maximum Speed Law with a number of exceptions (such as the posting of short stretches of 60-mph speed limits where Interstates transition from urban to rural or vice-versa).

Virginia law does not prescribe a fixed minimum speed limit, although a statute does authorize the posting of such limits where traffic and engineering studies indicate that they would be appropriate.

Finally, Virginia law permits differential daytime and nighttime speed limits following a traffic engineering investigation. As of February 2009, no such differential speed limits are in place in Virginia.

Wisconsin

The state of Wisconsin's speed limits are set out in statutory law but may often be modified by the maintaining government entity. In addition to a basic speed rule, Wisconsin law specifies certain occasions where reduced speeds are required including—and not limited to the approaches and traverses of rail crossings, winding roads, roads where people are present, and the crests of grades. Although there is no numeric minimum speed limit, state law prohibits the impediment of traffic by unreasonably slow speeds. Vehicles which lack rubber tires filled with compressed air have a hard limit of 15 mph.

The state of Wisconsin has four default speed limits. 15 mph limits apply in school zones, near parks with children, and in alleys. 25 mph default speed limits apply, unless modified by the managing authority, on "service roads" within corporate limits. Within municipal boundaries and in areas of dense urban development a 35 mph limit is in effect unless another speed limit is indicated. The entry to such an area is to be marked by speed limit signs. Outside of built-up areas (these include denser business, industrial or residential land uses according to the relevant law) a 55 mph limit is effective in the absence of other indications.

Along with the aforementioned default speed limits, there are other statutory speed limits which more often require signs to be effective. 65 mph limits on freeways and expressways require signs to be effective. The default speed limit on these types of roads is 55 mph as they do not directly interact with the built-up environment. In the densest urban districts a statutory 25 mph limit is effective when adequate signage is used, as are 35 mph limits in areas of light development. The same applies to 45 mph limits on highways designated as "rustic" roads. However, "an alleged failure to post [such a speed limit sign] is not a defense to a prosecution" in the case of such statutory limits.