Interstate 25


Interstate 25 follows the Front Range of the Rocky Mountains in New Mexico, Colorado and Wyoming. The mostly four-lane freeway joins the capital cities of Santa Fe, Denver and Cheyenne. I-25 also serves Albuquerque, New Mexico's largest city and Pueblo and Colorado Springs in central Colorado.

High Priority Corridor

Interstate 25 is part of High Priority Corridor 27: Camino Real for its entire length.

Parallel and Historical U.S. Routes

Interstate 25 replaced all of U.S. 85 from Las Cruces, New Mexico, north to Denver, Colorado. The freeway also replaced U.S. 87 from Raton, New Mexico, northward to its terminus in Buffalo, Wyoming with the exception of a parallel stretch between Glenrock and Casper. U.S. 85 parallels the freeway again in the Cheyenne vicinity. These U.S. routes are generally not co-signed in New Mexico or Colorado, but U.S. 85 and U.S. 87 are well-signed in Wyoming.

Other overlaps with U.S. routes in New Mexico include U.S. 60 north from Socorro, U.S. 285 near Santa Fe, U.S. 84 from Santa Fe east to Las Vegas and U.S. 64 at Raton. Within the Centennial state, U.S. 160 accompanies I-25 north from Trinidad to Walsenburg and U.S. 24 overlays I-25 at Colorado Springs. Within Wyoming, U.S. 26 runs in tandem with I-25 west from Dwyer to Glenrock while U.S. 20 ties in from Orin to Glenrock.


Interstate 25 through New Mexico replaced or directly overlaid all of U.S. 85 from Las Cruces north to the Colorado state line north of Raton. The first section to open ran from Socorro to Belen. Overall upgrades to U.S. 85 for I-25 were completed through the state in 1980.4

The Big I

A $270 million investment in the form of interchange reconstruction culminated in 2002 with the completion of the "Big I" construction project. This 24-month road work commenced July 2000 with the rebuilding of Interstate 25 ramps and overpasses in and around the junction with Interstate 40. This involved the replacement of left-hand entrance and off-ramps with new high-speed flyovers. In addition nearby frontage roads expand to two lanes and continue through the Big I area to improve traffic flow.

This photo shows the "Big I" interchange in Albuquerque from eastbound Interstate 40 at the junction with Interstate 25. Photo taken 03/31/05 by Jeff Royston.

Expansion of the freeway by one lane per direction was also accomplished. All of this was necessary to upgrade a substandard interchange that was designed to handle 40,000 vehicles per day (vpd). Current counts see around 300,000 vpd. These figures coincide with a population boon in the area and outward expansion of the city and suburbs. The original Interstate 25/40 junction, known as "The Crossroads of the Southwest," was constructed on the premise to move military personal and other long distance traffic through the Albuquerque metropolitan area. Daily commuter traffic interests were not factored into the original interchange design.2

For a history of the completion of Interstate 25 in Colorado, visit Interstate 25 @ AARoads.

Colorado Springs Metropolitan Interstate Expansion: COSMIX

Interstate 25 was also improved through the Colorado Springs area. As of March 2006, the Holland Park Noise Barrier and bridges over Ellston Street were completed. Projects continued to include widening and modernization of the freeway at the Bijou Interchange/Colorado Avenue, from Fillmore Street to Garden of the Gods, the section near North Nevada Avenue (Business Loop I-25) and Rockrimmon, and from Woodmen to North Academy. Completion of Colorado Springs Metropolitan Interstate Expansion (COSMIX) occurred by December 2007.


The largest multi-modal transportation project in Colorado history, T-Rex, started in September 2001. With origins dating back to 1944, the predecessor of Interstate 25 was the Platte Valley Drive Road. The $33 million project broke ground on November 16, 1948 and encompassed 11.2 miles. The road became known as the Valley Highway. Between Evans Avenue and 52nd Avenue, the freeway opened on November 23, 1958. Traffic counts topped at 33,000 vpd. By 1964, construction commenced for Interstate 225 with a design capacity of 50,000 vpd. This freeway opened fully between Interstate 70 and Interstate 25 on July 21, 1976. Both facilities were well over capacity with the Valley Highway at 230,000 vpd and Interstate 225 at 120,000 vpd in 1998. Traffic volumes were consistent in both directions of travel. This was based upon the fact that Denver has two major employment hubs: the Central Business District to the north and the Southeast Business District to the south. These factors set the tone for the T-REX construction project.

T-REX stands for Transportation Expansion Project and involves the Interstate 25/225 corridors. In 1992 studies began on how to handle the burgeoning transportation woes the Valley Highway entailed. The problem resulted in the partnership of the Colorado Department of Transportation (CDOT) and the Regional Transportation District (RTD), which is responsible for the Denver light rail system. The two agencies commissioned the Southeast Corridor Major Investment Study (MIS) to handle the growing dilemma. By 1995 several options were in consideration. They included the construction of new freeway lanes, the double-decking of existing freeway lanes, and construction of heavy rail, construction of monorail, and various other mass transit related options. By 1997 the Denver Regional Council of Governments (DRCOG) adopted the MIS recommendations. Those included 19.7 miles of new double-track light rail, 13 new light-rail stations, expansion of travel lanes to coincide with interchange improvements and bridge replacement projects, and HOV lanes among other concepts. Environmental Impact Studies, commenced in 1998, were completed in 18 months. Funding issues were addressed in 1999 and a Record of Decision signed in March 2000.3

Interstate 25 was expanded to four lanes per direction between Logan Street and Interstate 225. Two lanes in each direction were also added to Interstate 25 from Interstate 225 to the Colorado 470/E-470 junction, bringing this portion of highway to ten overall lanes of width. Interstate 225 saw expansion to six overall lanes between Interstate 25 and Park Road at Aurora. Eight interchanges were reconstructed, including the southern terminal of Interstate 225. The highway aspect of the project entailed $795 of the overall $1.67-billion project. To mitigate time concerns, a design-build scheme was implemented to the overall project. This allowed construction and design to take place simultaneously.

Similar projects using this form of engineering occurred with the Colorado 470/E-470 project and Interstate 15 reconstruction in Salt Lake City. Light rail lines were added along the west side of Interstate 25 and down the median of Interstate 225. A new highway lighting system was also put in place. The new fixtures use 1,000-watt lamps on 65-foot poles placed every 370 feet within the freeway median. Additionally sound barriers were also placed at certain locations within the project zone. Intelligent Transportation Systems (ITS) added during the T-REX project included ramp meters, variable message signs (VMS) and closed circuit cameras. The goal was to have the project completed on or before June 2008. Fortunately, accelerated construction resulted in a late 2006 completion date, 22 months ahead of schedule.3

The North Forty

Due to increasing development and rise in traffic volumes, expansion of Interstate 25 was slated to occur along a 40-mile stretch north of the capital city. The $370 project was broken into four phases, the first of which incurred the southernmost seven miles of the project area, covering the alignment between Colorado 7 and 52. This $73 million segment involved safety and capacity improvements. Construction ran between November 2001 and early 2005. Included in Phase One was an expansion of Interstate 25 from four to six lanes, reconstruction of the Weld County 8 interchange and removal of a railroad overpass to the north. The overall scheme allows for the addition of HOV lanes.

Phase Two entailed widening of Interstate 29 from Colorado 52 to Colorado 119. $36-million in road work on this element of the North Forty took place between November 2006 and June 2009. Phase Three widening of Interstate 25, between Colorado 119 and 66, expanded the freeway to six lanes and replaced five bridges during work from September 2007 and July 2009. Future work will widen Interstate 25 northward to Colorado 14 at Fort Collins.1

For a history of the completion of Interstate 25 in Wyoming, visit Interstate 25 @ AARoads.

Highway Guides

Southern Terminus - Interstate 10 - Las Cruces, New Mexico
Perspective from Southbound Interstate 25
The left lane of Interstate 25 transitions onto eastbound Interstate 10 toward El Paso, while the right lane transitions onto Interstate 10 west to Deming, Lorsburg, and the state of Arizona. Photo taken by Jeff Royston (05/27/04).
Perspective from Eastbound Interstate 10
The right lane of eastbound Interstate 10 transition onto northbound Interstate 25, while the left lanes continue east (south) on Interstate 10 en route to El Paso. Photo taken by Jeff Royston (05/29/04).
Perspective from Westbound Interstate 10
Interstate 10 westbound approaching Interstate 25 north. Photo taken by Jeff Royston (12/00).
Perspective of Interstate 10 westbound at Interstate 25 north. Photo taken by Travis Zeal (8/00).
Northern Terminus - Interstate 90 - Buffalo, Wyoming
Perspective from Northbound Interstate 25 and U.S. 87
End shield on north Interstate 25. The actual end of the designation is ahead, where the distant sign bridge is located (see below photo). Photo taken by Dale Sanderson (3/01).
Close-up of the sign bridge on Interstate 25 north at the terminus. Photo taken by Dale Sanderson (3/01).
Perspective from Eastbound Interstate 90
North beginning of Interstate 25 from eastbound Interstate 90 near Buffalo, Wyoming. Note that U.S. 87 follows Interstate 90 northwest and Interstate 25 south. This is the only tri-level stack interchange in Wyoming; the other major Interstate-to-Interstate (25 to 80) connection is currently a cloverleaf. Interstate 25 ends here, at Junction Interstate 90, just north of Buffalo. Photo taken by Dale Sanderson (3/01). Also thanks to Jim Teresco for information.
Perspective from Westbound Interstate 90 and Southbound U.S. 87
Eastbound Interstate 90 and Southbound U.S. 87 approaching Junction Southbound Interstate 25 and U.S. 87 (Exit 56B). Not signed here is Exit 56A, Junction Business Loop I-25 and Business Loop I-90 for the town of Buffalo. Photo taken by Rich Piehl (07/18/02).
Westbound Interstate 90 and Southbound U.S. 87 at Exit 56A, Junction Business Loop I-25 and Business Loop I-90, Buffalo. The next exit (Exit 56B) is for Southbound Interstate 25 and U.S. 87, one-half mile. Photo taken by Rich Piehl (07/18/02).
Southbound U.S. 87 splits off Westbound Interstate 90 to continue its southerly journey via Southbound Interstate 25. This marks the northern terminus of Interstate 25. Although not visible from this angle, this is a triple stack interchange. Photo taken by Rich Piehl (07/18/02).
Gore point signage for Southbound Interstate 25 as seen from the transition ramp from eastbound Interstate 90 onto southbound Interstate 25/U.S. 87. Photo taken by Rich Piehl (07/18/02).


  1. The North Forty Project. CDOT.
  2. Big I Project Information New Mexico State Highway & Transportation Department.
  3. T-REX CDOT.
  4. U.S. and Interstate Highways in New Mexico (Steve Riner).

Page Updated July 2, 2015.

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