United States Road Network

By | December 26, 2022

The Interstate Highway network.

The ‘High Five Interchange’ in Dallas, Texas.

According to wholevehicles, the road network in the United States is extensive, with approximately 11.5 million kilometers of public roads, two-thirds of which are in urban areas. This includes approximately 108,000 kilometers of highways, which are largely formed by the Interstate Highways, but also by other roads, such as US Highways and state highways. There are also many parkways in the east, especially around New York. Since 2013, the United States has the second largest highway network in the world, before that it had the largest highway network in the world for a long time, but the rapid growth of China ‘s highway network made China overtake the United States on December 31, 2013.

In addition to highways, the United States also has a very large network of 2×2 divided highways. These are roads with mostly separate lanes, at least 2 lanes in each direction, but with level crossings. In rural areas, many of these roads do not have traffic lights or roundabouts, so that, in combination with a higher maximum speed, they actually function as at-grade motorways. The United States has 144,000 miles of these 4-lane or more-lane roads outside of urban areas. Including the Interstate Highways, the United States has nearly 250,000 kilometers of roads with at least 4 lanes of traffic. Including urban roads, the United States has approximately 360,000 kilometers of road with a minimum of 4 lanes.

Road type Length
Interstate Highway 78,019 km
Other freeways 30,056 km
4 lane arterial (rural) 144,443 km
4 lane arterial (urban) 107,026 km

Road management

Roads in the United States are administered by the federal government, states, counties, townships, and cities. Although nationwide road numbering is in the form of the Interstate Highways and US Highways (sometimes incorrectly referred to as “Federal Highways”), these roads are under state control, but are eligible for federal funding. The United States Department of Transportation is the federal department that deals with transportation. However, the US DOT does not manage roads itself. Every state has a Department of Transportation or local variant thereof. These manage the network of state highways, which also includes the Interstate Highways and US Highways. Counties manage the county roadsand municipalities manage municipal roads, often only within built-up areas.

The exact distribution of who manages which roads varies by state. Some states have a Department of Transportation that manages almost all public roads. In a small number of states, there are no county roads at all. In such cases, the state controls a disproportionate share of all roads. It is often seen that roads of little importance should not be in the control of a state, but the practice differs from state to state. In most states, the Department of Transportation manages the primary and secondary highway networks, dividing it into Interstate Highways, US Highways, and State Highways. In addition, there are occasional other designations, most prominently the Farm to Market Roads in Texas.

The federal government manages a small number of roads through federal agencies, such as the federal National Park Service manages roads in national parks, and the Bureau of Indian Affairs (BIA) manages roads in Native American reservations.

A small number of roads are under private management, such as a relatively small number of toll roads. These are often under concession, and not owned by private companies. In rural areas there are often private roads, these are often unpaved, but sometimes publicly accessible, whether or not at an entrance fee (toll).

Interstate Highways

Wyoming ‘s Interstate 25.

The Interstate Highways are the national highway network of the United States and were created in 1956. The network covers 77,000 kilometres, about three quarters of all motorways in the country. In principle, all Interstate Highways have been developed as a freeway, but not all freeways are Interstate Highways. The Interstate Highways must meet the design requirements of Interstate Highways, which are stricter than standard freeways, the main disqualification of freeways that cannot become Interstate Highways are narrower emergency lanes or low headroom. Freeways can often be upgraded with relatively small investments so that they meet the design requirements.

Interstate Highways run in all states, but are not signposted in Alaska. In addition, there is a different road numbering in Hawaii. The system of the 48 contiguous states is numbered in one network. The Interstate Highways are numbered in a grid, with odd routes running south to north, with numbers increasing from west (I-5) to east (I-99). The even routes run from west to east, with the numbering increasing from south (I-2) to north (I-96). Not all numbers are in use and a small number of numbers are used twice in different parts of the country. The numbers ending in x0 and x5 are considered the primary routes and are often the longest routes.

It is prescribed that Interstate Highways and US Highways cannot have the same number in one state. Within this numbering system, the numbers would converge in the center of the United States. Most even numbers in the 50 and 60 series are therefore skipped to avoid confusion with US Highways.

The network of the main routes (one or two digits) is supplemented by auxiliary routes or auxiliary routes (three digits). These numbers are based on the main route they split off or cross. Of the three-digit numbers, the last two numbers are based on the main route, and the first number indicates the type of connection, an even-numbered three-digit Interstate Highway is usually a bypass or bypass, and a three-digit, odd-numbered Interstate Highway is a spuror tangent that no longer returns to the main route. These numbers are reused state by state. A number like I-295 can therefore appear several times in the different states. Three-digit Interstate Highways can run through multiple states, this is especially true of Interstate Highways that run around cities on a state line. I -275 forms Cincinnati ‘s beltway, passing through three states, Indiana, Kentucky, and Ohio. All auxiliary route numbers of I-90 are allocated in New York State (I-190 to I-990).

Interstate Highways can also be referred to as Intrastate Highwaysforms, which are main one- or two-digit routes that pass through only one state. There are quite a few examples of this. Three-digit Interstate Highways are very often “intrastate” and therefore are not considered anomalies. Violations can also occur in the road numbering system, for example a number that is well positioned in the network. An (infamous) example is I-99 in Pennsylvania, which is west of I-95, when the system says it can’t and should have been east of it. Despite the grid, there are also a number of routes that deviate in wind direction from the direction the number suggests, an example is I-69 in Michigan, which is a north-south number, but the highway bends east for a long stretch. Sometimes routes intersect, such as I-89 starting east of I-91.

US Highways

US 6 in Nevada.

The US Highways were introduced in 1926 and were the first national road numbering system in the United States. They were introduced at a time when states had also just introduced their first road numbering. Many states have therefore renumbered their state highways in the late 1920s and 1930s due to the introduction of US Highways.

The network of US Highways is much denser than that of Interstate Highways. Particularly in the east there is a very dense network of US Highways, but also in the west there are predominantly more US Highways than Interstate Highways, with the exception of California, where almost all US Highways were deleted in 1964 during a renumbering.

The US Highways vary in construction standard, from simple two-lane roads to wide freeways in metropolitan areas. In the Midwest and South, many US Highways are constructed as a 2×2 divided highway and supplement the network of Interstate Highways with relatively high-quality roads. There are so few intersecting roads and towns on the High Plains that these 2×2 divided highways function as level freeways, with a similar speed limit.

The road numbering system of US Highways is similar to that of the Interstate Highways, with odd routes running south-north and even routes west-east, with the difference that the numbering of the US Highways increases from east to west and from north to south, so the other way around than the Interstate Highways. The three-digit routes are parallel routes or branches of main routes. In many cases, three-digit routes are relatively long, ranging from several hundred kilometers to routes over 2,000 kilometers in length.

US 20 is the longest US Highway in the United States and runs for 5,415 kilometers from Newport, Oregon to Boston, Massachusetts. This is technically interrupted in the Yellowstone National Park in Wyoming, but is physically a through route. Originally US 6 was the longest US Highway and ran from Long Beach, California to Provincetown, Massachusetts and was originally about 5,615 kilometers long.

The 1926 numbering is still valid today, but many routes were added and other routes merged in the 1930s, especially in the western United States. Until the 1960s, the US Highways were responsible for most of the through traffic in the country. In the 1960s to 1990s, many US Highways were partially or completely scrapped after the completion of an Interstate Highway over or parallel to the US Highway in question. Most of the cuts were in the western United States because the Interstate Highways here are often built right next to or directly over the old US Highway, where this was often not possible due to the population density in the east of the country. For example, a well-known route cut was the section of US 40between San Francisco and Salt Lake City, which became I-80, and US 80 between San Diego and Dallas, which became I-8, I-10 and I-20. But perhaps the most imaginative route cut was US 66 ‘Route 66’ which ran from Santa Monica, California to Chicago and was scrapped in 1985.

State Highways

Nevada State Route 159.

Every state has a network of state highways. The naming varies slightly per state, state route and state highway are the most common, but state road or trunk highway are also terms that occur. State highways usually form the secondary road network, but the implementation varies from dirt roads to wide freeways. Some of the busiest roads in the United States are state highways. A network of 2×2 divided highways has been constructed in many states. Not infrequently, state highways are also included. Specifically, the Dallas-Fort Worth, Los Angeles, Miami, Minneapolis, New York City,Phoenix, San Francisco, and Seattle have an extensive network of freeways that are state highways.

The density of the network of state highways varies by state. Not only because of the population density, but also because it differs per state how large the share of all public roads is that is managed by the state. For example, in states like Louisiana, North Carolina, Virginia, and West Virginia, nearly all public roads are state highways, resulting in a network of tens of thousands of miles of state highways per state.

The numbering of state highways varies by state. In many states, all road types, Interstate Highway, US Highway, and State Highway are numbered in one system, but that is not always the case. The way road numbers are assigned also varies, from random to chronological to clustered and to a grid. Often it is not possible to deduce from the number how important a road is. In several states, three-digit state highways have been developed as freeways.

Reference routes

A reference route is a type of state highway whose road number is not signposted. These occur in multiple states, but the best known are the unnumbered parkways in upstate New York, primarily around New York City, but also in the Buffalo and Rochester area.

Farm to Market Roads

The FM 1092 in Houston.

Special in Texas are the Farm to Market Roads. These are state highways but have a different classification, they can be a Farm Road or Ranch Road. These types of roads are almost always asphalted and very occasionally have been developed as freeways. Due to the advancing suburbanization around major Texas cities, many FM Roads have been classified as Urban Road since 1995, however they remain signposted as Farm Road.

County Roads

Clark County Hwy 215 in Las Vegas.

The county roads or county highways are the roads in the administration of the counties. Almost all states are divided into counties, except Louisiana, where they are called a parish, and Alaska, which has boroughs. The county is the highest tier of local government. The extent to which counties are involved in road construction varies by state, in some states county highways are only responsible for the most minor roads and dirt roads, while in others county highways are a more important network. Some large counties with more than a million inhabitants often have a professional county highway department. County roads are almost never freeways.

Toll roads

Florida’s Turnpike at Yeehaw Junction.

Express lanes on Interstate 405 in Washington around Seattle.

The vast majority of the road network in the United States is toll-free. Nevertheless, there are a fairly large number of toll roads. The toll roads have their origins in the late 18th and early 19th centuries, when so-called turnpikes were built, especially in the eastern states. A toll was charged for wagons to be allowed to pass. Calculated for inflation, these were high toll rates. They were not very popular, but they were often the only good roads in the states. In the mid-19th century, the importance of the turnpikes diminished with the rise of the railways. Most of the remaining turnpikes were purchased by the states in the early 20th century and made toll-free.

At the end of the 1930s, a new form of turnpikes, modern motorways on which tolls were levied, emerged. The first was the Pennsylvania Turnpike which opened in 1940. Shortly after World War II, a number of states began developing toll roads. The longest was the toll road from the East Coast to Chicago, in the form of the Pennsylvania Turnpike, Ohio Turnpike, Indiana Toll Road, and Chicago Skyway which opened mostly about 1955. This was the United States’ first long highway. Other pre-Interstate Highway toll roads were the Dallas-Fort Worth Turnpike, the New Hampshire Turnpike, Maine Turnpike andConnecticut Turnpike in New England, the New Jersey Turnpike and Garden State Parkway in New Jersey, the New York State Thruway, the Kansas Turnpike, the Turner Turnpike in Oklahoma and the West Virginia Turnpike.

The creation of the Interstate Highway system in 1956 made the construction of toll roads obsolete, federal funding allowed to build an immense network of highways that did not require tolls. Still, several toll roads were built in the late 1950s and 1960s, including Florida’s Turnpike, the Jane Addams Memorial Tollway and the Ronald Reagan Memorial Tollway in Illinois, and part of the Massachusetts Turnpike. In two states, Kentucky and Oklahoma, a large number of toll roads were still built during that time. Those in Kentucky later became toll-free.

In the 1980s, federal funding began to dry up as most of the Interstate Highways were completed. At the same time, cities in the southern United States began to grow rapidly. In Florida and Texas in particular, a large number of toll roads were built that mainly run within urban areas. Some more recent toll roads have also been built around Chicago.

A new trend since 2000 is the construction of express lanes (toll lanes) on existing highways. The first were the 91 Express Lanes in the Los Angeles area in 1995. Express lanes have since become popular to fund major reconstructions, particularly in the southern, western, and eastern United States. However, in much of the United States there are no express lanes at all. Cities with toll lanes include Atlanta, Baltimore, Dallas-Fort Worth, Houston, Los Angeles, San Diego, San Francisco, Seattle, andWashington, D.C..

The toll roads are usually state-owned, directly under the department of transportation or a separate agency, a regional public toll road operator, or – more rarely – under a concession. Major regional toll road authorities include the Harris County Toll Road Authority in Houston and the North Texas Tollway Authority around Dallas-Fort Worth.

Almost all toll roads that have been developed as freeways offer some form of electronic toll collection (ETC). Originally, each state developed its own system that was not interchangeable with that of other states. Eventually, the E-ZPass group grew into the largest electronic toll system in the Northeast, East, and Midwest of the United States. From 2014, more and more systems are interchangeable. At secondary toll points, especially some smaller bridges outside the main road network, electronic toll collection is often not offered. Users of electronic toll collection often receive a discount. In many metropolitan areas, more than 80% of transactions are with ETC, driving more and more administrators to open road tollingwhere there are no longer any physical toll gates. The toll can then only be paid electronically with a transponder or registration toll (which is often more expensive).

Differences with Europe

The State of Iowa Grid Network.

The Astoria-Megler Bridge (US 101) between Oregon and Washington.

In addition to the obvious differences, such as the signage, there are also layout differences. Markers can be either white or yellow, often the outer mark will be white, and the center mark will be yellow. A yellow marking separates driving directions, also on roads with separate lanes. In some areas, such as in Los Angeles, so-called “Botts Dots” are used, which are actually not markings, but reflective spheres. These date from a time when reflective road paint was not yet used. Since 2017, the so-called “Botts Dots” are no longer used in California.

It is common for major roads in urban areas to have more lanes in each direction (usually a maximum of 3) and which do not always have a central partition. These roads often have exits from businesses and homes. Cyclists are rarely encountered, but almost all roads in urban areas have footpaths. In addition, an asphalt strip can be installed between the driving directions that can be used for left-turning traffic in both directions, this is a so-called center turn lane. You do not have to stop in the through lanes. The marking of this differs, sometimes it is clearly marked with positioning strips, other times it is just a strip with only arrows to the left.

Roundabouts are rarely used in the United States, but they are becoming more common. What does occur regularly, especially in the east, are the so-called traffic circles, which are comparable to Dutch traffic circles, with or without traffic lights.regularly. In residential areas there are many 4-way stops, which means that one has to stop at every branch of an intersection. Whoever comes first gets to go first. This is also done to ensure that people do not drive too fast on the long straight roads. This is especially the case with roads in a grid pattern. Newer suburban areas rarely have a grid pattern, but are set up more playfully. Not all intersections with major roads have traffic lights. Turning left can be especially problematic. This is done so that traffic does not have to stop every 80 meters.

On the highways, traffic behaves differently than in Europe. Officially, a keep-your-lane system does not exist, and it is “keep right unless to pass”. However, this is rarely used in urban areas. Overtaking is done on both the left and the right and trucks do not always drive on the right, but are also often found in the middle lanes. Trucks usually don’t drive all the way to the left on roads with more than 2×3 lanes. Trucks drive considerably faster than in Europe and often overtake other car traffic. In addition, the right lane in suburban areas is mainly for decoration and for oncoming traffic, even when it is quiet people do not always drive in the right lane. This varies greatly by area. Some states do keep to the right, especially on 2×2 lane highways.

On highways with many exits in urban areas, the ramp often flows directly into the exit of the next exit, even if there is more than a kilometer between them. These are by no means always separated from the continuous strips by block marking. However, you can see from the signage that it is not a through lane because it says ” exit only ” with black letters on a yellow background. Exit lanes are much shorter than one sees in the Netherlands, usually one has to send the vehicle into the exit in one movement. This is mainly seen in rural areas where there are no queues at the exit. This system is also seen, for example, in Denmark.

It is difficult to give an unambiguous description of road behavior in the United States, as driving behavior can differ greatly per state and even per agglomeration. For Europeans, it can take some getting used to driving in the US.


Interstate 35W in Minneapolis.

Interstate 93 in Boston, constructed as part of the ‘Big Dig’.

The 29-kilometer Atchafalaya Bridge (I-10) in Louisiana.

Interstate 64 in St. Louis, Missouri.

The Alaska Highway in Alaska.

stack nodes around Austin, Texas.

The history of the road network dates back to the 17th and 18th centuries, when the first turnpikes were built in the northeastern United States. These were (semi-) paved roads for which toll had to be paid. Until the beginning of the 20th century, road management was the responsibility of local authorities, municipalities and counties in most states. Most states assumed primary responsibility for road network development between 1905 and 1915, often through the creation of a state highway commission or equivalent. In the early years, hardly any money was available for roads and before 1920 in many states almost all roads outside built-up areas were still unpaved. The first high-quality road in the country was the Long Island Motor Parkwayat New York City in 1908.

Crucial was the Federal Aid Road Act of 1916, which made federal money available for the development of the road network. This was $75 million, a huge sum at the time (about $1.5 billion today), with states allowed to qualify 6% of their road networks. From then on, especially the states west of the Appalachian Mountains began to asphalt their first roads. Several new items were introduced in the 1920s. There was no road numbering, only the car trails were signposted or marked to varying degrees until the 1920s. Many states introduced the first road numbering, or established a network of state highways, in the first half of the 1920s. Many states also introduced a fuel tax in the 1920sintroduced to finance the development of the road network.

Important was the introduction of the US Highwaysin 1926. In many western states, there was no clear plan as to which roads should be prioritized for asphalting. This changed with the US Highways, as the major thoroughfares of these states became clear. In the next 10 years, most US Highways have been paved. During the economic depression of the 1930s, much federal money became available for infrastructure under the New Deal, often implemented by the Works Progress Administration (WPA). The states on the Great Plains, in particular, paved thousands of miles of road in the 1930s. Also, many states at that time really took control of the road network and expanded their network of state highways by thousands or even tens of thousands of kilometers, mainly by taking over and asphalting roads from the counties. The size of the network of state highways was by no means always in proportion to the size of the state or population. At that time, many states took roads in governance that are very secondary in nature, and would be better off ifcounty road.

In the 1920s and 1930s, parkways began to be built around New York City under the supervision of Robert Moses. This became the prelude to a national network of highways. In the 1930s, a large network of parkways and expressways was built in the New York City area. Also, in the late 1930s, work began on the nation’s first long-haul highway, the Pennsylvania Turnpike, which opened in 1940, although it can be argued that the Merritt Parkway in Connecticut is an older example of an interurban highway connection.

From 1941, the United States became involved in World War II. The financing for roads dried up quickly, almost all investments had to have a direct interest in the warfare. Many cheap asphalt roads in the 1930s fell into disrepair. These were often the so-called ‘oiled roads’, where there was only a thin layer of oil over a gravel roadis constructed to make them smoother and dust-free. However, they did not have much carrying capacity. In 1944, plans were made for large-scale federal funding for roads after the war, but this proved to be far from sufficient, as the condition of the American road network deteriorated faster than expected. During World War II, the Highway Departments were mainly concerned with planning the post-war road network, but did almost nothing about new construction or maintenance. Very few new roads were opened between 1941 and 1945.

In the second half of the 1940s, several cities opened their first freeways, such as in California and Texas. The construction of highways in the 1940s and 1950s was mainly linked to urban areas, few proposals were made for a national network of motorways. One exception, however, was a series of turnpikes between the East Coast and Chicago, which were rapidly constructed in the mid-1950s, such as the New Jersey Turnpike, extensions of the pre-existing Pennsylvania Turnpike, the Ohio Turnpike, and the Indiana Toll Road.. In most states with larger cities, the first highways had opened in the mid-1950s. Construction progressed slowly, however, because municipal authorities were usually responsible for expropriation costs, which were high at the time because the first highways were often built through built-up areas, and an expensive right-of-way had to be purchased.

However, that changed drastically with the creation of the system of Interstate Highwaysin 1956 by President Eisenhower. Billions were made available for the development of an immense network of freeways in the United States. There was little discussion of usefulness and necessity, and many freeways opened in the 1960s and 1970s, including on the High Plains and in the interior of the western United States, where there was very little traffic at the time and often today. is. The Interstate Highway system gained momentum in the 1960s and thousands of miles of new highways were opened every year. By the late 1970s, most routes had been completed, with the last missing links often opening in the early 1980s. In the western United States, many villages depended on passers-by for their income, and these long held back the construction of the last missing bypasses, as in Arizona, Nevada, New Mexico and Texas. In the early 1990s, several stretches of Interstate Highway were opened that have been described as the last missing links, such as the opening of I-90 at Wallace, Idaho in 1991 and I-70 through Colorado’s Glenwood Canyon in 1992.

Beginning in the 1980s, states began to experience reduced federal funding, increased maintenance targets, and declining tax revenues. However, many states, especially in the southern United States, grew very quickly and there appeared to be a great need to widen existing highways and build new highways, especially in metropolitan regions such as Atlanta, Dallas-Fort Worth, Houston., Orlando and Phoenix. To this end, various new sources of financing have been tapped. These were often toll roads, but in some urban areas this is also toll-free, through an increase in the sales tax, such as in Phoenix.

After the completion of the original Interstate Highway plan, several new routes have been developed, partly by upgrading existing freeways to Interstate Highway, but also by planning completely new routes. For example, examples of upgrades to existing routes were I-39 and I-41 in Wisconsin. But all-new routes included I-11 between Phoenix and Las Vegas, I-22 between Memphis and Birmingham, I-26 between Tennessee and North Carolina, I-49 between Shreveport and Kansas City, and I-69 between Mexico and Canada.

A problem from the 1990s onwards was the rapid increase in the cost of road projects. Infamous was the ‘Big Dig’ in Boston where I-93 was constructed in a tunnel, and the project eventually suffered significant cost overruns. The same problem occurred with the replacement of the eastern span of the San Francisco – Oakland Bay Bridge in California and the replacement or major renovation of bridges in the New York area. A dichotomy also emerged in the United States, with hardly any investment in the road network in the northeast and along the west coast from the late 1970s, while states in the south and southeast carried out major road projects. Especially in TexasSince 2000, a large volume of mega-projects have been carried out, especially in the metropolitan areas.

Speed ​​limits

There is no national speed limit in the United States. States may determine these individually. There is also no general limit per road type, the maximum speed is determined per road section and is therefore customised, although there are guidelines. For example, there is no general speed limit within built-up areas or outside built-up areas as in Europe, not even per state.

The speed limit is usually 30 – 45 mph within built-up areas and 50 to 65 mph on regular single-lane roads outside built-up areas. Motorways are generally allowed to drive between 65 and 80 mph. The highest speed limits are generally found in the more sparsely populated states of the Midwestern and Western United States, with the exception of the states bordering the Pacific Ocean.

In the United States, there is not necessarily a different limit for trucks. Many states allow trucks to travel between 70 and 80 mph (110 – 130 km/h). However, many drivers and transport companies do not drive that fast. Speed ​​limiters are not mandatory, but are regularly used for safety reasons and to save on fuel costs.

The lowest speed limits for truck traffic are found in California where the speed limit is 55 mph. The lowest speed limits on freeways are found in Hawaii, Oregon and several states in the northeast of the country. The highest speed limit is on one highway in Texas (SH 130) where the speed limit is 85 mph (137 km/h). In Texas, some single-lane roads are allowed to drive up to 75 mph (120 km/h). Since 2010, an increasing number of states are allowed to drive at 80 mph (130 km/h).

Quality of roads and bridges

The United States is frequently in the news because of the poor quality of its infrastructure. However, there are major regional differences. Much of the bad roads are only in a few states. In 2019, 5% of urban Interstate Highways and 2% of rural Interstate Highways were in poor condition. In that year, 25% of poor Interstate Highways were concentrated in just three states. Poor condition urban roads are also largely concentrated in a small number of states, with California, New York, New Jersey & Rhode Island leading for many years as the worst roads, with 20-30% of urban roads in poor condition. However, there are also 21 states where less than 7% of city roads are in poor condition.

The quality of the bridges has improved greatly since the 1990s. In 1992, 124,000 bridges were still classified as ‘structurally deficient’ 22% of the total. In 2020, there were still 45,000 bridges, 7% of the total. The greatest number of bad bridges is in the control of the counties. These are usually bridges in the local road network.


Congestion on the Santa Ana Freeway in Los Angeles.

The interchange between I-10 and I-45 in Houston.

Seattle ‘s Interstate 5.

Some cities are notorious for traffic jams, such as Los Angeles and New York City. However, it is not just traffic jams that matter. In particular, the cities in the central part of the United States, in the Midwest, have little congestion, and if there are any traffic jams, the delay time is limited to a dozen minutes. American cities dominate the list of least congested major cities in the world. In the 2015 TomTom Traffic Index, of urban areas with more than 800,000 inhabitants, almost all cities with a low ranking (less congestion) were American, of the 45 cities with more than 800,000 inhabitants with the least congestion, 43 were in the United States located.

The older cities in the east tend to have a less developed highway network, especially when it comes to current design requirements and number of lanes. This problem is present in Washington, Philadelphia and New York, for example. In Los Angeles, the enormous population size plays a major role in the number of traffic jams. In general, the traffic jams are comparable in size to the Randstad. The largest city with the fewest traffic jams is Kansas City, and Los Angeles with the most traffic jams. However, the longest average travel time is in New York.

Outside the major cities, the highways are often quiet very quickly. Outside the built-up area of ​​an agglomeration, the traffic intensity often drops to 20,000 to 30,000 vehicles per day. Only some highways that run a short distance from two larger cities can be busier, but connecting highways are rarely wider than 2×2 lanes the full length between two cities.

Traffic volumes are often high, this is because US cities are usually much larger than European cities. Intensities above 200,000 are not uncommon in the largest cities, although the number of roads with an intensity higher than 300,000 is already a lot more limited. The busiest highway has historically been Los Angeles’ I-405 with 390,000 vehicles per day, but the Downtown Connector in Atlanta has overtaken that listing. I-10 in the west of Houston also has very high traffic volumes.

Busiest highways

away Location intensity Year
Downtown Connector in Atlanta 404,000 2016
Katy Freeway in Houston 387,000 2016
I-405 at Seal Beach (Los Angeles) 377,000 2016
I-5 at Santa Ana (Los Angeles) 366,000 2016

Per region


In the northeastern states, the New England region, outside the city of Boston and the metropolitan area of ​​Connecticut, there are almost no traffic jams. There can be congestion in Boston, as well as in Hartford, Providence and the suburban region of New York City. This is largely due to some incomplete routes that have not been completed due to the freeway revolts, creating an unnecessary bundling of traffic flows, often with bottlenecks.

The Mid-Atlantic region has a lot of traffic jams, especially in New York City and Philadelphia. In New York, the high population and the outdated highways mainly play a role, also to a lesser extent in Philadelphia. In both cities, due to opposition and spatial planning, it is almost impossible to widen highways without very high costs. The prioritization of public transport over the road network also plays a role in New York state. As a result, there are major differences in the metropolis of New York between the states of New York and New Jersey.

In the so-called “Rust Belt” there are a number of cities that have lost a lot of population and have a highway network that is dimensioned for many more inhabitants. There are also few files here. Some examples are Akron, Buffalo, Cleveland, Detroit, Rochester, Syracuse and Youngstown.


The Midwest is one of the regions in the United States with few traffic jams. There are some exceptions, such as the Chicago, Minneapolis, and Detroit area where there are quite a few traffic jams, but other cities such as Kansas City, St. Louis, Cleveland, Indianapolis, and Cincinnatihardly have to deal with traffic jams. Here, cities have been able to grow proportionally in all directions without too many obstacles, so that traffic flows are more evenly distributed than in areas with large bodies of water or geographical obstacles such as mountains. In the western Midwestern states, low population numbers also play an important role.


In the southern United States, varying images can be seen. On the one hand, there are coastal cities such as New Orleans and Miami that do not have commensurate traffic flows due to the presence of coastline and other geographic obstacles. On the other hand, there are cities such as Charlotte, Atlanta, Houston and Dallas where there are quite a few traffic jams, but no extreme traffic jams. Smaller agglomerations have far fewer traffic jams. However, the region is growing very fast, which means that traffic flows are increasing considerably every year. This is not always adequately addressed by the various DOTs. Again, in the more midwestern cities like Oklahoma City and Louisville, there are almost no traffic jams at all.


In the west a mixed picture. On the one hand, there are the central mountain states where few people live and there are few large agglomerations. Cities such as Denver and Phoenix do not have major traffic problems, but the coastal cities do have major traffic jams due to their geographical location between large bodies of water and mountain areas. These are for example Los Angeles, Portland, San Francisco and Seattle. In Los Angeles in particular, the relatively limited highway network according to the size of the population plays a role. Due to the expropriation of buildings and the high density of buildings, major road widening here is a costly affair. Portlandhas much more congestion than other US cities of its size. In Honolulu, Hawaii, there are also major traffic problems due to the location between sea and mountains.

Holiday crowds

In contrast to Europe, the United States does not have the typical summer holiday crowds. The holidays are more spread out and many people travel by plane to their destination. Although there is an increased traffic volume at the start of the school holidays, this is in no way proportionate to the extreme crowds in France, Germany, Italy or the Alps.

The busiest traffic around a holiday is usually around Thanksgiving, when people go to visit relatives. The Christmas period also has a strongly increased traffic volume, as well as around some other holidays. Short breaks or long weekends are popular to get to a cottage on the coast or in a lake area. Relatively few Americans take the car for 2 or 3 weeks on summer vacation. Motorhomes and caravans (also called a recreational vehicle or travel trailer) are often seen as something for retirees.

Road numbering

For the main article, see Road numbering in the United States.

The road network is numbered according to a grid pattern in the highest layers, the Interstates and the US Highways. State Routes often crisscross a state, rather than following a grid pattern, with the exception of Midwestern states where a full grid pattern already exists naturally.

Interstate Highways

The interchange between I-95, I-395 and I-495 at Washington in Virginia.

Wyoming ‘s Interstate 80 at Green River.

The Interstate Highways are numbered in a grid pattern. There is no Interstate 1, 2, 3 and many other numbers, although according to the system it could be. The closer the highway network, the more numbers are used. In the eastern United States, for example, there are hardly or no numbers left in some series, while numbers are still available in the middle and west.

The odd numbers are highways that run from the south to the north. The main routes run per 10 from 5. and in many cases are highways that run throughout the country. The numbering increases towards the east. I-5 runs along the west coast and I-95 along the east coast. There are also odd numbers that don’t end in 5, but these are often shorter in length, although that’s not always true. Odd numbers may also be so-called diagonal connections, which run in a northeasterly or northwesterly direction.

The even numbers are highways that run from west to east. The I-2 is the lowest number here and runs in Texas. As with the odd numbers, the main east-west connections run by 10 from 10. The I-10, I-20, I-30 to I-90 are all longer east-west connections. The lowest numbers run along the south coast and the Mexican border to the highest numbers closer to the Canadian border.

The three-digit numbers are numbered according to their main route, with the last two digits being the number of the main route, and the first digit being the first in the series. For example, I-310 is the third route of I-10. For an even first digit, these are usually ring roads, and for odd first numbers, these are tangential or inductive roads. Since some major routes are thousands of miles long, the 3-digit series may be repeated state by state. For example, almost all combinations of the I-5 in California and the I-90 in New York have already been used. This could cause problems in other states. Cross-state numbers may only be used once per state. Like I-275 in both Kentuckyif Ohio is located, the number I-275 may not be used again elsewhere in any of those states.

Around the Great Lakes region, and especially near the city of Chicago, the system is not quite right, because Lake Michigan runs far south, for example, I-90 and I-94 are pushed far south, making them at the same height, or even double-numbered or run further south than I-80, which does run well according to the system. Also, in a few places numbers have been used that should actually be east of the previous number, but have been placed west of it. For example, these are I-99 in Pennsylvania and I-97 in Maryland. In general it can be said that the system has been applied correctly.

Although Interstates are highways that run through several states (hence the name), there are also major Interstate routes that remain within one state, these are called Intrastate Interstates, examples of which are the I-17 and I-19 in Arizona and the I- 37 and I-45 in Texas.

Shared Interstate Highways

In some cases, a main route is split into two routes, for example when passing through an urban area with two main centers. These cases are quite exceptional. Most notably, I-35 divides twice, into I-35E and I-35W in Dallas-Fort Worth and Minneapolis-St. Paul. This is currently the only Interstate number where this phenomenon occurs, but it used to be more common, with I-80 being the most notable example. These have now been replaced by other road numbers.

Additional Interstate Highways

There are also additional Interstate Highways, usually the so-called Business Routes and Spurs. These are signposted on a green shield instead of the usual blue and red shield. A Business spur or walk down branches of the main route, serving city centers. An example of this is I-80 in Sacramento, where the main route runs north of downtown, and Business I-80 passes through downtown. Another example is at Spartanburg in South Carolinawhere I-85 goes north of town, and Business I-85 through downtown. The road characteristics are not always a highway, sometimes the number also runs through the underlying road network. In some cases, the Business Routes were previously the main route, with the latter being moved later and a Business Route may fill the number gap. A Business Loop is the most common, spurs are fairly rare.

US Highways

The Golden Gate Bridge (US 101) in San Francisco.

The Superstition Freeway (US 60) in Phoenix, Arizona.

The reverse of the Interstates applies to US Highways. Even and odd they are routed the same, but they run in the opposite direction. For example, US 2 starts as the northernmost east-west route and US 1 as the easternmost north-south route. Since the system of Interstate Highways and US Highways would converge in the middle of the United States, there is no I-50 or I-60. It is also intended that no US Highways and Interstate Highways of the same number should exist in one state. However, there are a few exceptions to this.

Shared US Highways

In some cases there are US Highways that split into an East/West or North/South section. This is usually rare and branches off the main route are considered important to number the same as the main route. This only happens 10 times in the whole country. Previously, however, there were a lot more, and they have been around since 1926. Usually a main route branches off into both an E/W or N/S route, but sometimes only an E, W, N or S route branches off. AASHTO has been trying to eliminate this numbering, seen as imperfections, since 1934. Usually they get a State Route number, and new shared numbers are no longer approved.

Additional US Highways

An extra US Highway is different from a shared US Highway, namely a so-called ALT or BYP, an Alternate or Bypass. There are also BUS (Business), TRUCK (truck) and some other extras, such as a Scenic, City, Thru, Spur and even Temporary. ALT, BUS and BYP extras are the most common. Alternative numbers form an alternative route to the main route, which in most cases costs hardly more kilometers and has the same function. Business route are often additional numbers that connect business centers with a main route. Usually main routes pass through the business centers by themselves, but this is not always the case. A Bypass is a bypass or intersection of the main route. The main routes often run through the various centers, but this is not the fastest route across the entire road number. A Bypass can then occur.

State routes

State routes or state highways are numbered per state, and the same road numbers occur continuously in other states, sometimes even connecting. Road numbers come in one, two and three digit combinations. However, as a rule, state routes with the same number as a US Highway and Interstate Highway do not exist within one state. There are also exceptions to this. In Texas there is another additional road number layer, consisting of the Farm to Market Roads. These can have up to 4 digits. There are also county roads in the various states. As a rule, these are no more than local roads. County roads are almost never roads with highway characteristics. Only in exceptional cases are county highways or farm roads designed as freeways.

Reference Routes

Reference routes exist in the state of New York. These are road numbers for name-only highways, such as the many Parkways around New York City. These reference route numbers are not signposted via regular signage, but are mainly administrative, and are often only displayed on reference markers. In some other states, all numbered roads also have a reference road number, such as in Florida. In other states, there are also reference numbers for unnumbered highways, usually named toll roads.

Indication of numbers

Road numbers are variously designated in spoken and written language in the United States. What is special is that in Southern California people speak of ‘the 5’ and ‘the 10’, while this is less common elsewhere in the country. In written language, an Interstate Highway is usually abbreviated to I-5, I-10, I-990, etc. In Texas, however, they have a different spelling, where they shorten it to ‘IH 10’ and ‘IH 35’. US Highway numbers are usually indicated as US 50 or US 281, although occasionally a hyphen is used as with the Interstate Highways, so US-50 and US-281.

State highways have more variation. SR or SH are used alternately as an abbreviation, in Minnesota sometimes also TH (trunk highway). In addition, the state abbreviation is often used, such as OK-1 or PA-500 (Oklahoma and Pennsylvania). In addition, some states use another variation, such as Wisconsin, which uses ‘WIS’, Wyoming, which uses ‘Wyo’, and Michigan, which uses ‘M-‘. In addition, numbers are often referred to by the name of the state, for example ‘Illinois 10’ or ‘Louisiana 40’.


See US signage for the main article.

Signage on Interstate 95 in Maryland.

American signage is quite different from European signage. In addition to Control Cities, the Americans often work with cardinal directions, which is a consequence of the grid network, which is usually perfectly situated north-south and east-west. In larger cities, one can also find signage that only speaks of “Thru Traffic” or “To Interstate xx”. The size of Control Cities can still differ, with prefer not to indicate cities at very large distances, as in the west and midwest larger cities can sometimes be many hundreds to more than a thousand kilometers apart. As a result, smaller, seemingly insignificant places can often also be seen as a control city. Sometimes a smaller control city close by is preferred to a large city further away.

Because American cities often have many (sometimes more than a hundred) suburbs, it is impossible to indicate all of them individually, no matter how large they are. An additional problem is that in some metropolitan areas (New York, Chicago, Atlanta) the suburbs are quite small, more often not exceeding 30,000 inhabitants per city. As a result, references such as “western suburbs” are also common. There are hardly any distance signs in urban areas, more frequent outside them, but often do not show very large distances.

Turns to residential areas or districts are hardly known in the United States. Urban areas have very many exits, and it is impossible to give all exits a somewhat unique name. For example, there are more than a thousand exits in the Los Angeles metropolitan area. Usually reference is made to the major road that crosses the highway, for example “Grand Avenue” or “Sunset Boulevard”. In addition, many highways in the United States have names, often named after a geographic point, such as a river or city, as well as historical persons. These names are sometimes better known than the road number, and are also called that in everyday speech. For example, they are more likely to say “Hollywood Freeway” or “The one-oh-one”, than the US 101.Parkways only a reference number, which is only used administratively, and is not signposted. One always speaks of the road name.

On highways one can often encounter the sign “exit only”, this is used at exits where there is no parallel lane. Often the slip lane of the on-ramp merges into the slip lane of the next exit, and then “Exit Only” is used to distinguish the lane from the through lanes. Furthermore, portal signs on highways do not always put all arrows at the lanes, but they refer to “left 5 lanes” or “right 2 lanes”. There are also occasional left turns. The so-called HOV lanes also often have separate lanes and exits, these are indicated in a different way. At junctions with other highways, the wind directions are often also indicated on the portal signs, such as “East” or “North”, accompanied by the road number plate,

Turns are indicated by the turn number: the numbering is done both sequentially and remotely. Turns in urban areas are usually indicated well in advance. Signs in the median strip often announce the distance to the next 3 to 4 turns. This is useful when you have to move a number of lanes in heavy traffic. At the so-called “Gore point” there is also a sign with “Exit xx”.

Commonly used names such as “Avenue”, “Boulevard”, “Street”, “Drive”, “Freeway”, “Parkway” and “Expressway” are usually abbreviated to Av, Blvd, St, Dr, Fwy, Pkwy and Expwy. Both the word Freeway and Expressway are used in the United States. Freeway is commonly used in the western states, and expressway in the eastern states (with a few exceptions), and in the midwest it varies by state.

Junctions are usually announced by a sign with the road number plate, followed by the wind direction, and below that the control city. Junctions are also included in the exit numbering. There are almost never road numbers on distance signs, because people are expected to know which road they are on. However, there are often trailblazers to be seen, a pole with the road number plate on it. In rural areas, portals are often not used. In the west, some exits do not lead to any town or hamlet, and are therefore sometimes referred to as just ” farm road ” or “ranch road”. They try as much as possible to give all rural exits a unique name.

At intersections one can often see a pole with several road number plates accompanied by the wind direction, and the arrow which direction that is in, especially in the less populated areas, where extensive signage is not considered necessary.

Traffic rules

In the United States, there is no federal law governing traffic regulations. The states determine this individually. The traffic rules sometimes have minor differences by state, but are generally consistent with each other. Rules such as seat belt use and the use of telephones and other mobile devices are also determined by state. Here too, the rules are largely similar, in 49 of the 50 states the use of a seat belt is mandatory. However, wearing a seat belt in the back seat is not required in most states. There are campaigns such as ‘click it or ticket’. The traffic signs are standardized via the Manual on Uniform Traffic Control Devices (MUTCD) that is used throughout the United States, with or without some local deviations.

Drivers license

The age at which you can drive for the first time also varies by state. One usually starts with a ‘learner’s permit’, followed by a ‘restricted license’ and finally a ‘full license’. The age at which it is allowed to drive with a learner’s permit varies from 14 to 16 years. A restricted license can be obtained if one is between 15 and 16.5 years old, in one state (New Jersey) that is 17 years. A full license can be obtained between the ages of 16 and 18, with the exception of Maine, where one must be 21 years of age. The driver’s license is issued by the Department of Motor Vehicles, each state has such an agency, which usually falls under the Department of Transportation.

Driving under the influence

Driving under the influence is called driving under the influence (DUI) or driving while intoxicated (DWI). It is illegal in all states to drive with an alcohol percentage of more than 0.08%, although some states also issue fines for driving with an alcohol percentage of 0.05%. In addition, lower limits often apply to truck drivers or bus drivers. Enforcement varies by state, often there are campaigns such as ‘booze it and lose it’.

Speeding violations

In contrast to Europe, there are few speed cameras in the United States, red light cameras are even illegal in some states. Speeding violations in the United States are mainly fined by standing or a mobile speed camera. Every state has a highway patrol patrolling the roads.

Road safety

The number of road deaths in the United States since 1900.

In 2014, there were 32,675 road deaths in the United States. This equates to 103 per 1 million inhabitants. By 2015, this had risen to 35,200 deaths, or 109 per 1 million inhabitants. Road safety in the United States is significantly worse than neighboring Canada, which recorded 52 road deaths per 1 million inhabitants in 2014. The United States also performs significantly worse than Australia, New Zealand and the European Union average. In 2014, only one EU country (Latvia) had more road deaths per 1 million inhabitants than the United States.

The number of road deaths per 100 million vehicle miles.

state 2012
Massachusetts 0.62
Minnesota 0.69
Connecticut 0.75
Washington 0.78
New Jersey 0.79
Rhode Island 0.82
Utah 0.82
New Hampshire 0.84
California 0.88
Maryland 0.89
Illinois 0.91
New York 0.91
Virginia 0.99
Ohio 1.00
Colorado 1.01
Oregon 1.01
Wisconsin 1.04
Nevada 1.07
Vermont 1.07
Nebraska 1.10
Georgia 1.11
Idaho 1.13
USA average 1.13
Iowa 1.16
Maine 1.16
Missouri 1.21
Alaska 1.23
North Carolina 1.23
Delaware 1.24
Hawaii 1.25
Florida 1.27
Kansas 1.32
Pennsylvania 1.32
Alabama 1.33
Wyoming 1.33
Arizona 1.37
Tennessee 1.42
New Mexico 1.43
Texas 1.43
South Dakota 1.46
Oklahoma 1.48
Mississippi 1.51
Louisiana 1.54
Kentucky 1.58
Arkansas 1.65
North Dakota 1.69
Montana 1.72
South Carolina 1.76
West Virginia 1.76


The number of road deaths per 100 million vehicle miles between 1900 and 2015.

On September 13, 1899, Henry H. Bliss was killed in New York City when he was hit by an electric taxi at the intersection of West 74th Street and Central Park West. This was the first fatality in the United States and possibly the Western Hemisphere.

The number of road deaths increased sharply in the 1960s and 1970s, peaking at 54,589 deaths in 1972. The number of road deaths fell relatively little between 1975 and 2005 due to the strong population growth and the accompanying growth in traffic. Between 2005 and 2010, the number of road deaths fell sharply from 43,500 to 33,000, but the decline has stagnated since then. The popularity of the smartphone and its use in traffic is an increasing cause of traffic accidents. In 2013, distraction was the cause of 18% of accidents involving injury.


Transport statistics

The table below shows the modal split, expressed as a percentage of the total number of travelers.

Country Car Carpool Public transport
United States 83.5% 11.0% 5.5%
The Netherlands 76.7% 7.7% 15.6%

The table below shows the modal split, expressed in passenger kilometres.

Country Car Public transport
United States 88.6% 11.4%
Netherlands 87.4% 12.6%

The table below shows the commuting times in minutes.

Country Car Carpool Public transport
United States 23.8 28.0 47.7
Netherlands 27.0 34.0 53.0

The table below shows the number of vehicle kilometers per inhabitant per year (2010).

Country vehicle miles
United States 15.424
Netherlands 7.491

The table below shows the modal split of the number of tonne-kilometres of freight transport (2007).

Country Truck Rail Water
United States 35.7% 49.3% 15.0%
European Union 75.1% 18.4% 6.5%
Netherlands 52.3% 5.1% 42.6%

Road surface statistics

TRIP has conducted research into how large a percentage of the urban road network is in poor condition. Nationally, 27% of urban roads are in poor condition. However, at the regional level there are big differences, the worst road networks are mainly found in the northeast and the west coast.

agglomeration % bad
San Francisco 73%
Los Angeles 73%
Concord, CA 62%
Detroit 56%
San Jose 53%
Cleveland 52%
San Diego 51%
New York City 51%
Honolulu 51%
San Antonio 49%
Milwaukee 46%
Riverside/San Bernardino 46%
Tulsa 45%
New Haven, CT 45%
Oklahoma City 45%
New Orleans 42%
Seattle 42%
sacramento 42%

Public transport

Public transportation in the United States accounts for approximately 2% of all trips and 5% of home-to-work trips. Public transportation in the United States is dominated by only a small number of major cities, most notably New York City, Boston, Chicago, Washington, and San Francisco. In other cities the share of public transport is minimal. As in Europe, public transport in particular has a higher share of trips to and from city centres. But city centers only account for 7% of all employment in urban areas with more than 3 million inhabitants. This results in a low share overall. By car, 65% of the jobs in metropolitan areas can be reached within 30 minutes. In contrast, only 10% of the runways can be reached within 60 minutes by public transport.

Table: The share of jobs in the agglomeration that can be reached within 60 minutes by public transport:

agglomeration (MSA) Part
Atlanta 2.5%
Austin 4.1%
Baltimore 11.2%
Boston 11.7%
Charlotte 5.5%
Chicago 7.2%
Dallas 3.1%
Denver 14.2%
Detroit 3.2%
Houston 4.6%
Kansas City 4.5%
Los Angeles 7.0%
Miami 5.3%
Minneapolis 7.8%
New York 14.6%
Philadelphia 7.3%
Phoenix 6.1%
Portland 14.4%
San Antonio 10.2%
San Diego 9.0%
San Francisco 17.5%
San Jose 21.5%
Seattle 11.1%
St. Louis 5.5%
Tampa 4.6%
Washington 11.7%

In addition, the US Census Bureau mainly uses statistics for public transportation as a share of commuter-to-work traffic. However, commuting is only a part of the total transport, so that the actual share of public transport is considerably lower than when only commuting is considered. For example, in New York the share of public transport on commuting is 31.5%, while the share of public transport on all travel motives is only 11.5%.

Table: The share of public transport for home-work and all travel motives

agglomeration (MSA) share of home-work share total
New York 31.5% 11.5%
San Francisco 17.2% 6.6%
Chicago 12.0% 3.4%
Seattle 9.3% 3.4%
Washington 13.7% 3.2%
Boston 13.6% 2.7%
Philadelphia 9.7% 2.4%
Baltimore 6.5% 2.3%
Portland 6.9% 2.3%

United States Road Network