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