Colorado Road Network

By | October 13, 2022

The road network in Colorado is not very extensive, the Interstate 25 highway connects all major cities of the state. In addition, Interstate 70 and Interstate 76 run east-west through the state. The high altitude of some roads is striking, such as the I-70 in the Rocky Mountains at an altitude of 3,401 meters. This can make I-70 impassable in winter and even in summer due to ice and snow storms. In addition, the highest road in the United States is located in Colorado, the Mount Evans Scenic Byway, which goes up to 4,310 meters. Only slightly lower is the Pikes Peak Highway.

Due to its low population density, the state of Colorado does not have a dense road network. Especially in the High Plains in the east, the roads are quite far apart, often connecting only small villages and hamlets. These roads often handle less than 1,000 vehicles per day. In parts of the Rocky Mountains it can be a bit busier due to recreational traffic to the winter sports areas. Here are a large number of high mountain passes.

Colorado is known for the many tourist roads in the state, especially in the Rocky Mountains. There are numerous ski resorts in Colorado and the state has roads through wild nature and high mountain passes. In the winter there is quite a lot of snow, but Colorado has very little perpetual snow, although many mountains are still covered with snow until June or July. There are no glaciers in Colorado like in the Alps. However, the roads in Colorado are much higher than in the Alps, because the valleys are also much higher. Many valleys are higher than the highest mountain passes in the Alps. The city of Denver, which from the Rocky Mountains looks like ‘located in the lowlands’, is located at 1,600 meters above sea level.

  • Bittranslators: State overview of Colorado, including geography, economy, population and history as well as introduction to major cities of Colorado.

Road management

The state highway authority is the Colorado Department of Transportation, abbreviated CDOT or CODOT. CDOT manages a state highway system of 14,713 kilometers, in which 3,429 bridges are located. CDOT has its origins in the State Highway Commission that was formed in 1909 and merged into the State Highway Department in 1917. In 1968, the name was changed to the Colorado Department of Highways (CDOH) and became the current Colorado Department of Transportation in 1991.

Interstate Highways

The Interstate Highways are the main thoroughfares for through traffic, but large parts of the state are far from the highway. I-25 forms the north-south route along the Front Range, where nearly all of Colorado’s major cities are located. This makes it the busiest highway in the state. I-70 runs east-west through the Rocky Mountains and has many beautiful routes such as in the Glenwood Canyon and around the Eisenhower Tunnel. East of Denver, however, the road crosses the barren High Plains. I-76 runs northeast from Denver and connects to the state of Nebraska. Around Denver is a beltway that was once designated as I-470, but today has no Interstate status, and is numbered SH 470 or E-470. I-225 forms a north-south highway through Aurora, one of the largest suburbs in the United States. I-270 runs through Commerce City in northern Denver.

  • Deluxesurveillance: Nickname of Colorado as The Centennial State. Also covers geography, history, economy, politics and administration of the state.


The first highway in Colorado was the Denver-Boulder Turnpike in 1952, today US 36. In the late 1950s, the first sections of Interstate 25 in Denver and Colorado Springs were opened. I-25 was built fairly quickly after that, and was completed in 1969, when the last section between Trinidad and Walsenburg in the south of the state was opened. In 1966, a significant portion of I-76 opened from Denver beyond Sterling. A significant number of sections of Interstate 70 were also opened in the 1960s, but it took quite a while to complete the highway, partly due to the very mountainous nature of western Colorado. In 1973, the Eisenhower Tunnel, the highest point in the United States, opened Interstate Highway System at 3,401 meters above sea level. In 1975, I-70 through eastern Colorado was complete, but a section to the west took longer. On October 14, 1992, I-70 opened through Glenwood Canyon, completing the final link. Since the 1980s, a number of new highways have also opened around Denver, most notably the ring road, which should have become I-470, but never materialized. Ultimately, the ring was largely constructed as the E-470 toll road. Colorado Springs remains one of the largest single highway cities in the United States.

US Highways

The US Highways are the major highway network in areas where there are no Interstate Highways, which are large parts of the state of Colorado, especially through the mountains in western Colorado. Long-haul traffic with a destination and origin outside of Colorado will rarely use the US Highways, but traffic within Colorado and from Colorado to neighboring states often uses the US Highways. Most US Highways are single-lane roads through the mountains, some of which run over very high mountain passes. Some US Highways are designed as 2×2 divided highway, most prominently parts of US 50 in the south of the state. US 36 is a highway between Denver and Boulder. US 6 and US 285 are also short highways in Denver.

State Highways

The state highways (SH) of Colorado generally form secondary connections, the through roads are formed by the Interstate Highways and US Highways. Most state highways are relatively short, only a single connection is more than 100 kilometers long. The state highways are generally two-lane roads, in the east of the state these are long, straight roads, in the west of the state these are mountain roads with often many height differences. Several state highways have been freeway around Denver, most prominently SH 58 between Golden and Denver and SH 470 that forms part of the ring road.


From 1908, the first auto trails in Colorado were signposted. The state highways were formed in the early 1920s, the first concrete number plan dates from 1923, although there are also maps from 1919 with road numbers, but it is unclear to what extent these were signposted. The original 1923 system included 19 long-haul routes through Colorado, numbered SH 1 through SH 19, and secondary routes, numbered SH 51 through SH 181. Beginning in 1926, US Highways were first introduced, although several routes did not cross Colorado until the 1930s and 1940s. Initially they were double numbered with the state highways. From the 1950s, the first Interstate Highways were built there Bee. By the 1960s, such a large proportion of major state highways were double-numbered with US Highways that many state highways were chosen in 1968 to be scrapped. Many of the numbers SH 1 through SH 19 are today only brief remnants of the once cross-Colorado routes that formed them from the 1920s.

In 1939, the state of Colorado took control of hundreds of miles of local roads. These were only short spurs and connections in the countryside, which were massively numbered, in the series SH 20 to SH 49 and SH 190 to SH 378. A large part of these roads was transferred back to the lower roads 15 years later. governments; counties and municipalities. Some songs still exist today.

Toll roads

There are relatively few toll roads in Colorado. The most prominent toll road is part of the Denver Beltway, formed on the east by E-470 and on the northwest by the Northwest Parkway. Tolls are among the highest in the country. In addition, there are express lanes on I-25 in Denver and US 36 between Denver and Boulder that require tolls. Tolls also have to be paid for the touristy Pikes Peak Highway.

Traffic intensities

Traffic volumes are highest in the Denver area, especially the I-25 Corridor through the Front Range, which connects all major cities of the state. The highest intensity in 2014 was measured on I-25 at the interchange with I-70 in Denver at 261,000 vehicles per day. In the southern suburbs, however, an almost equally high intensity is measured. The highest intensity on I-70 is 207,000 vehicles per day in eastern Denver. The lowest traffic volume on an Interstate Highway was on I-76 in the northeast of the state at 6,100 vehicles per day.


Congestion occurs primarily in Denver and to a lesser extent around Colorado Springs. The towns along the Front Range are growing rapidly and the highways can’t always keep up with the strong population growth. The I-25 still has 2×2 lanes in many places, and is often congested there, especially between Pueblo and Fort Collins. In addition, congestion in Denver occurs on I-25 and I-70, especially where these highways converge. After a number of expansion projects on I-25, I-225 and US 36, the congestion has eased.

Road numbering

US Highways & Interstate Highways

The Interstate Highways and US Highways are numbered according to the national grid. The height of the number is not always indicative of its importance. For example, US 6 in Colorado has relatively little importance.

Interstate 470 was once planned to be a Colorado ring road. However, this never came about as such. The ring road was later built almost completely, but is numbered as SH 470, E-470 and the Northwest Parkway. As a result, Colorado only has two auxiliary routes, I-225 and I-270 in Denver, although I-270 is a direct extension of US 36 and adds little as an individual number.

State Highways

The state highways were first numbered in the early 1920s, after a numbering plan from 1923, although there is also a numbering on a map from 1919, but it was probably not signposted. State highways were numbered in series 1 through 19 for the cross-Colorado routes and numbers higher than 50 for regional routes. The numbering 20 to 49 was skipped at the time.

From the 1923 numbering of state highways, odd numbers 51 through 63 and 71 ran north-south across the East Plains in the east of the state, ascending from the border with the states of Kansas and Nebraska. The even numbers from 50 to 72 and a few odd numbers above were mostly in the Denver area and north of it. The higher numbers were clustered by region, although some numbers were also randomly assigned within the state. Road numbers above 160 are often short routes and spurs, many of which would not look out of place as a county road. Only a few state highways with a number between 159 and 402 are longer than 25 kilometers.

From 1926, the US Highways were introduced in Colorado, which in most cases were laid over existing state highways. From the 1950s, the Interstate Highways were added. At the time, the state highways and US/Interstate Highways overlapped each other, which resulted in a large number of long double numberings. In the 1960s there were so many that it was decided to scrap or drastically shorten many state highways in 1968. Since then, many of the original cross-Colorado routes from 1 to 19 have only been short connections. Partly due to the renumbering of 1968, the height of the road number is still little indicative of its importance. Relatively many numbers under 70 are short routes in the Front Range region, many of these routes are less than 30 kilometers long.

The road numbering of state highways was only sporadically adjusted after 1968, and was often customised. It was also decided that numbers of state highways were not allowed to appear if there is already a US Highway or Interstate Highway. These are skipped, which is common in many US states. After 1968, on the basis of local necessity, the numbers between 20 and 50 were also partly assigned. These are often urban routes.

Road number shield

Colorado has a road number shield with the state flag and number. It is the only road number plate in the United States with 5 colors (black, white, blue, red & yellow). Most states use road number plates with 2 or sometimes 3 colors. This is a point of criticism, as is the fact that the road number is shown relatively small compared to the entire road number shield, although this is more common in the United States.

County Roads

County roads in Colorado are not uniformly numbered. Some counties don’t have numbered roads, only street names, especially in the fragmented counties around Denver. Some counties have numbers, other counties have lettered roads.

There are no townships in Colorado, which means that all roads outside the city limits (built-up areas) are controlled by the counties, except those controlled by the state of Colorado.

Colorado Road Network