Interstate 225 Colorado

Interstate 225 Colorado
I-225 south at I-25 - Denver, CO

Passing below the flyover carring traffic from I-25 south to I-225 north and RTD light rail bridges linking the H-Line and R-Line with the E-Line and F-Lines along I-25 at Hampden South in Denver. The R-line runs northward along nearly the entire length of I-225 to Peoria Station. 08/11/16


The lone branch route from Interstate 25, I-225 constitutes a commuter freeway from Hampden South in Denver to Aurora. The loop joins Interstate 25 north from Greenwood Village to I-70 east by Peña Boulevard to Denver International Airport (DEN). I-225 passes by Cherry Creek Reservoir / State Park and Aurora Mall in Arapahoe County and the University of Colorado Anschutz Medical Campus in Adams County.

Interstate 225 was historically the main southeastern bypass, but a second bypass freeway was created with the completion of the E-470 Toll Highway. The area along I-225 was originally not developed, but as population grew and new housing developments were constructed, I-225 became a busy corridor. Additionally, business travelers use I-225 and E-470 as the most direct route from the Denver International Airport (DEN) to the Denver Tech Center.


The initial Interstate Urban Network proposed by the Colorado Department of Highways on February 6, 1958 outlined a circumferential route at Denver as Interstate A25. Route 25E was suggested for the loop on April 3, 1958 based upon the Route Numbering Committee assigning north, south, east and west to route numbers for certain segments of the Interstate system, as it would provide an easterly bypass for I-25. Further correspondence between the Department of Highways and the American Association of State Highway Officials (AASHO) in July 1958 renumbered Interstate 25E as I-225.

The Bureau of Public Roads then suggested on November 10, 1958 that the loop north of I-70 be designated as Interstate 425 instead of I-225, and that the loop in the southeastern quadrant of the Denver area remain as Interstate 225. AASHO concurred and authorized the Department of Highways to officially designate I-425 and I-225 in a letter dated February 5, 1959.

The Department of Highways agreed with a suggested change by the Bureau of Public Roads to relocate the planned west end of Interstate 80S from I-70 to I-25. This resulted in I-80S overlapping with approximately one mile of the planned route of I-425 west to I-25. Since the northern terminus of I-425 changed from a connection with I-25 to one with I-80S, the route would no longer link with Interstate 25. The Department of Highways indicated that the northern section might be more properly designated as Interstate 270 in a letter to AASHO on February 6, 1959. AASHO found the proposal to be satisfactory, but also suggested that I-80S and I-270 might be cosigned west to I-25 for the convenience of the traveling public.

Construction for Interstate 225 got underway at the interchange with I-70 in May 1964. The first mile opened from Colfax Avenue (U.S. 40-287) south to Colorado Highway 30 (E 6th Avenue) in June 1966. The succeeding section opened was the 2.1 mile segment from Mississippi Avenue (Exit 7) to Colorado Highway 83 / Parker Road (Exit 4) on September 3, 1971. Following that was the 1971 to May 27, 1975 construction of I-225 southwest 2.5 miles to Yosemite Street (Exit 2B).1

Completion of Interstate 225 took place on May 21, 1976 with the freeway opening of 1.2 miles from Yosemite Street west to I-25. Improvements were already underway in 1976 to the north at both the bridges over Mississippi Avenue and at the interchange with 6th Avenue.1

Route Information

  • North End – Aurora, CO
  • South End – Denver, CO

  • Mileage – 12.46

  • Cities – Denver, Aurora

  • JunctionsI-25 I-70

Source: December 31, 2021 Interstate Route Log and Finders List

Southeast Denver, CO - 1960s Map
Undated map of Denver showing Interstate 225 south from Yale Avenue.

The initial design for Interstate 225 at south Denver included an access road from the freeway near Cherry Creek Reservoir to Hampden Avenue (old U.S. 285) and a simple wye to I-25 south and from I-25 north.

Denver, CO - 1972 Map
Denver – 1972 Colorado Official Highway Map

Interstate 225 extended south to SH 83 (Parker Road) by September 1971. A directional T-interchange joined the freeway with I-70 at the north end.

Subsequent bridge replacements were made along I-225 at Sand Creek by August 1990 and over Smith Road and the Union Pacific Railroad as part of a reconstruction of the freeway between 30th Avenue and Smith Road. That $6.8 million project ran from October 1992 to August 1994. $4 million in work also underway from March to October 1994, reconstructed the interchange with I-70 and widened I-225 southward to Smith Road.1

Further work at the north end added a 1,967 foot long flyover from I-70 west to I-225 south at the cost of $18.2 million. The new ramp opened to traffic on April 23, 1994. $4 million construction from Fall 1994 to April 1995 also reconstructed ramps from I-70 east to I-225 south and from I-225 north to I-70 east. Work on the flyover from I-225 north to I-70 west followed from September 1997 to Summer 1998.1

Interstate 225 was further expanded to six lanes south from Colfax Avenue to Sand Creek from February 1996 to November 1997, and between 6th Avenue and Colfax Avenue by December 1997. A new interchange for Alameda Avenue (Exit 8) was completed in 2002, while construction on a flyover from SH 83 (Parker Road) north to I-225 south started in September 2000.1

The southernmost portion of Interstate 225 was incorporated in the greater Denver “T-REX” construction project. The $1.72 billion project expanded both I-25 and I-225 with additional lanes and light rail corridors. Work along I-225 widened the freeway to six lanes from I-25 north to SH 83 and reconstructed the interchange with Interstate 25.2 The overall six-year project was completed by late 2006.

 Photo Guides

North End I-70 US 36 – Aurora, Colorado

I-225 North at I-70

I-225 north at I-70 - Aurora, CO

A collector distributor roadway from 17th Place returns to Interstate 225 north one mile south of I-70. The six lane freeway crosses Sand Creek ahead. 08/11/16

I-225 north at I-70 - Aurora, CO

Traffic separates into a three lane ramp for I-70 west to the Montbello and Stapleton areas of Denver and a two lane exit for I-70 east to Denver International Airport (DEN), east Aurora and Bennett. 08/11/16

I-225 north at I-70 - Aurora, CO

The original directional T interchange with Interstate 70 was redesigned to eliminate left exit ramps. Flyovers for Exits 12A/B were built during the construction from 1994 to 1998.1 04/22/17

I-70 East at I-225

I-70 east at I-225 - Denver, CO

The initial sign for Interstate 225 south (Exit 282) appears at the Havana Street underpass. A $25 million project underway in May 2015 replaced the I-70 bridges over Havana Street here, made ramp and lighting improvements, and constructed a tunnel for the railroad adjacent to Havana Street.3 08/11/16

I-70 east at I-225 - Denver, CO

The succeeding exit joins Interstate 70 east with Peoria Street and the Stapleton industrial area. Interstate 225 south follows in one mile. 08/11/16

I-70 east at I-225 - Denver, CO

Three lanes serve commuter traffic headed south onto Interstate 225 through Aurora. 08/11/16

I-70 West at I-225

I-70 west at I-225 - Aurora, CO

The south end of Peña Boulevard, an access freeway to Denver International Airport (DEN), ties into Interstate 70 westbound within the exchange at Chambers Road, one half mile from I-225 south. 04/22/17

I-70 west at I-225 - Aurora, CO

A collector distributor roadway (Exit 282) separates from I-70 westbound for both I-225 south and Pecos Street. The c/d roadway departs just after traffic merges from Peña Boulevard south. 04/22/17

I-70 west at I-225 - Aurora, CO

Upgrades to the exchange with I-225 were made when Peña Boulevard was built. Peña Boulevard is named for former Denver Mayor Federico Peña, who was in office during the construction of the DEN Airport. Peña went on to be a Transportation Secretary for President Bill Clinton. 04/22/17

I-70 west at I-225 - Aurora, CO

The high speed flyover for Interstate 225 south through Aurora departs from the c/d roadway ahead of Peoria Street. 08/11/16

I-225 North End Throwback

I-70 west at I-225 - 2001

Replaced overhead for Interstate 225 at the c/d roadway for Exit 282. Photo by Dale Sanderson (04/01).

I-70 east at I-225 - 2001

2016 sign changes made at Exit 282 on I-70 east removed the Chambers Road overhead and replaced the panel for I-225 to show three lanes. Photo by Dale Sanderson (05/01).

South End I-25 – Denver, Colorado

I-225 South at I-25

I-225 south at I-25 - Denver, CO

The first guide sign for Interstate 25 appears by Dayton Station, 1.5 miles out. The R-line light rail runs between the roadways of I-225 southward from SH 83 to the south end. 08/11/16

I-225 south at I-25 - Denver, CO

Interstate 225 turns westward into Denver’s Hampden South neighborhood ahead of Tamarac Street and DTC Boulevard south to the Denver Tech Center. 08/11/16

I-225 south at I-25 - Denver, CO
I-225 south at I-25 - Denver, CO

Exits 1A/B separate for Interstate 25 north to University Hills, Baker and Downtown Denver and south for Greenwood Village, Centennial and Lone Tree. 08/11/16

I-25 North at I-225

I-25 north at I-225 - Denver, CO

Interstate 25 northbound enters the city of Denver north from SH 88 and Denver Tech Center just ahead of Exit 200 for I-225. 07/04/12

I-25 north at I-225 - Denver, CO

The entrance ramp from SH 88 (Belleview Avenue) at Denver Tech Center partitions with ramps for both I-25 north into Denver and I-225 northeast to Aurora. 04/22/17

I-25 north at I-225 - Denver, CO

TREX construction realigned the I-25 mainline so that north and southbound traffic travels side by side, with new distributor roadways added for the adjacent interchange with SH 88 (Belleview Avenue). 07/04/12

I-25 north at I-225 - Denver, CO

Ramps from I-25 north and SH 88 combine along Interstate 225 north through Hampden South in Denver and ahead of Cherry Creek Reservoir. 04/22/17

I-25 South at I-225

I-225 south at I-25 - Denver, CO

I-25 converges with Interstate 225 between the Southmoor Park and Hampden South neighborhoods in south Denver. 04/23/17

I-225 south at I-25 - Denver, CO

Interstate 225 arcs northeast from Exit 200 between Cherry Creek State Park and the Kennedy neighborhood in Denver to the city of Aurora. 04/23/17

I-225 south at I-25 - Denver, CO

Two lanes leave I-25 south at the directional T interchange with Interstate 225 north. I-225 uses Limon for the connection with I-70 east at the north end. 04/23/17

I-225 South End Throwback

I-25 north at I-225 - 2001

The roadways of Interstate 25 previously separated through the directional T interchange (Exit 199) with I-225 to accommodate left exit ramps for the southbound. Photo by Dale Sanderson (04/01).

I-25 north at I-225 - 2001

Exit 199 departed from I-25 north for Interstate 225 east to the city of Aurora. This ramp now joins a distributor roadway from SH 88 north. Photo by Dale Sanderson (04/01).

I-225 south at I-25 - 2001

Prior to the reconstruction during the TREX Project, a left exit ramp departed from Interstate 25 south for I-225 north to Aurora. The new ramp separates from the southbound mainline further north. Photo by Dale Sanderson (04/01).


  1. Interstate 225 – 50th Anniversary of the Interstate System. Colorado Department of Transportation (CDOT).
  2. “T-REX Project Fact Book.” Colorado Department of Transportation, January 2002.
  3. Colorado Department of Transportation (CDOT), project web page.

Page updated November 12, 2020.