Interstate 270 (Colorado)

I-270 begins at an interchange with I-25 in Welby and is concurrent with US 36. The speed limit through the first section is 45 mph (72 km/h).^[4][5] The freeway heads southeastward for about one mile (1.6 km), crossing over Washington Street and State Highway 224 (SH 224), but access is not provided to either road. Mileposts along I-270 reset to 0 at the I-76 interchange because it was the original western end of the Interstate.^[1][6] Since the I-76 interchange is close to both I-270's western end and the I-25/I-76 interchanges, some movements in the interchange are missing. Eastbound I-270 traffic cannot access westbound I-76 nor can eastbound I-76 traffic access westbound I-270. However, traffic on I-25 can access both westbound I-76 and eastbound I-270, thus completing the missing movements. The three interchanges work together by eliminating bottlenecks caused by redundant interchanges.^[7]

Beyond the I-76 interchange, the speed limit increases to 55 mph (89 km/h).^[8] The freeway heads southeast, comes to a westbound exit and eastbound entrance with York Street, and crosses the South Platte River^[9] into a commercial area in Adams County. I-270 enters the city of Commerce City,^[10] running roughly parallel with the nearby Sand Creek^[11] and crossing over SH 265 without an exit.^[12][13] Continuing through the city, the route comes to a cloverleaf interchange with Vasquez Boulevard, which carries US 6, US 85, and SH 2.^[14] The freeway heads eastward into Denver,^[15] where it has an exit at SH 35, a short highway which continues northward along Quebec Street for one mile (1.6 km).^[16] Quebec Street provides access for traffic heading to westbound I-70. The route ends shortly thereafter when it merges into I-70.^[7]

The freeway is maintained by the Colorado Department of Transportation (CDOT), who is responsible for maintaining and constructing transportation infrastructure in Colorado, including highways.^[17] As part of this role, CDOT periodically conducts surveys on their highways to measure traffic volume. This is expressed in terms of annual average daily traffic (AADT), which is a measure of traffic volume for any average day of the year. In 2009, CDOT calculated that as few as 56,500 vehicles used I-270 daily east of its western terminus at I-25 and as many as 89,600 vehicles used I-270 daily southeast of York Street in Commerce City.^[18] As part of the Interstate Highway System,^[19] the entire route is listed on the National Highway System, a system of roads that are important to the nation's economy, defense, and mobility.^[20]

The Colorado Department of Highways originally planned to use a single number, I-25E, for the entirety of Denver's eastern loop.^[21] The designation was changed to I-225 following correspondence with the American Association of State Highway Officials and split, with the northern leg becoming I-425 in 1958.^[22] The northern leg was then renumbered to I-270 on February 26, 1959, following a request from the Colorado Department of Highways to reflect that it would terminate at I-80S (now I-76) instead of I-25.^[23]

I-270 was constructed in several phases, beginning with a section from I-70 to Vasquez Boulevard. Following this section was another part of the freeway from Vasquez Boulevard west to I-76, and finally a section from US 36 to I-76. This last segment has undergone much more construction, including new bridges and ramps at interchanges.^[2]

Construction on I-270 began in 1965. The first portion cost about $2.7 million (equivalent to $18.1 million in 2023^[24]).^[2] It opened in 1968, connecting I-70 to Vasquez Boulevard. Two years later, another two-mile (3.2 km) segment connected the portion already in service to I-80S.^[2] I-80S became I-76 in 1976.^[25] Construction began on the section between I-76 and I-25 in April 1993 and was finished in September 1999, costing $11.4 million (equivalent to $19.6 million in 2023^[24]).^[2] The mileposts were already established when construction took place, so the route was not assigned new mileposts.^[1] Completion of this portion largely decreased traffic problems in the area.^[26][27]

The bridges along westbound I-270 over Washington Street were replaced and finished in the late 1990s, costing $12 million (equivalent to $24.7 million in 2023^[24]).^[2] By the end of 1998, the bridges over Clear Creek near the I-76 interchange were completed. In February 2000, a connection between westbound I-270 and westbound US 36 was completed,^[28] as was access between I-76 westbound and I-270 westbound.^[2][29] The eastbound section between US 36 and I-76, including new bridges over Washington Street and Clear Creek, was completed in March 2002 and totaled $8.5 million (equivalent to $13.8 million in 2023^[24]).^[2][30] Three years later, a flyover ramp was constructed connecting I-25 southbound to I-270 eastbound.^[2][31] However, access between I-270 eastbound and I-76 westbound still does not exist.^[32][33]

Citing its significance as a freight corridor, in 2002, the Denver Regional Council of Governments (DRCOG) recommended widening I-270 from four to six lanes by 2025,^[34] and it later identified widening I-270 and rebuilding the I-270/Vasquez Boulevard interchange in its 2040 Fiscally Constrained Regional Transportation Plan.^[35] CDOT also maintained an interest in widening the freeway through the 2000s and 2010s, though funding was not available.^[36][37] In October 2019, they listed the study and reconstruction of I-270 from I-76 and I-70 among projects to receive funding from Senate Bill 17-267; the reconstruction would include toll lanes, and toll revenue would be used to cover costs not paid by SB 17-267.^[38]

In early 2020, CDOT included widening I-270 between I-76 and I-70 in the first phase of projects of their 10-year vision.^[39] The High Performance Transportation Enterprise, a business within CDOT, additionally ranked I-270 fourth among its top priority corridors for managed lanes, placing it after three segments of I-25 in the Denver metropolitan area.^[40] CDOT began a National Environmental Policy Act (NEPA) study of I-270 in April 2020, scheduled to finish in late 2021^{[41][needs update]} but noted that budget cuts in response to the COVID-19 pandemic could affect the project.^[42]

• Colorado portal
• U.S. roads portal

Wikimedia Commons has media related to Interstate 270 (Colorado).

• SH 267 to SH 299 at the Highways of Colorado
• I-270 at the Interstate Guide