Colorado Highways: Interstate 25

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Location: South Front Range > Metro Denver > North Front Range
Length*: 298.87mi
S End: New Mexico border at Raton Pass (link to Steve Riner's site)
N End: Wyoming border north of Wellington (link to Andy Field's site)
Nationally: S End: Jct I-10 at Las Cruces, New Mexico; N End: Jct I-90 at Buffalo, Wyoming (1059mi)

Counties: Las Animas, Huerfano, Pueblo, El Paso, Dougals, Arapahoe, Denver, Adams, Broomfield, Weld, Larimer
Places: Trinidad, Walsenburg, Pueblo, Fountain, Colorado Springs, Monument, Castle Rock, Castle Pines North, Lone Tree, Centennial, Greenwood Village, Denver, Northglenn, Thornton, Broomfield, Mead, Loveland, Windsor, Fort Collins, Wellington

NHS: All Interstate Highways are by default part of the NHS. 

Freeway: Entire length (exit lists)

Business Routes:

• Unmarked spur to Aguilar
• Marked loop of Walsenburg

Roadways Names:

• I-25 is commonly referred to as The Valley Highway in metro Denver, due to it's history as being known as that when it was built. That name, however, is not "official" anymore and does not appear on any signs.

• John F. Kennedy Memorial Highway, New Mexico border to the north Pueblo County line
  
• Ronald Reagan Highway, in El Paso County

Scenic & Historic Byways:

Milepost Guide:

0.00: New Mexico border (begin I-25 in Las Animas County) 13.60: SH 12 interchange, Trinidad 14.85: US 160/To US 350/To SH 239/Goddard Ave interchange 34.09: BS I-25 interchange, Aguilar 39.10: Enter Huerfano County 49.00: BL I-25 interchange, south Walsenburg 50.05: US 160/SH 10 interchange 52.32: BL I-25 interchange, north Walsenburg 68.85: Enter Pueblo County 74.36: SH 165 interchange, Colorado City 94.76: SH 45/Pueblo Blvd interchange, Pueblo 97.91: BR US 50/Santa Fe Ave interchange 99.95: US 50 East interchange 101.38: US 50 West/SH 47 interchange 116.43: Enter El Paso County 127.86: US 85 interchange, Fountain 131.65: SH 16 interchange, Fountain 138.97: US 24 East interchange, Colorado Springs 139.74: SH 115/Nevada Ave interchange 141.13: US 24 West/Cimmaron St interchange 160.76: SH 105 interchange, Monument 163.32: Enter Douglas County, Monument Hill 184.21: US 85/Founders Pkwy/Meadows Pkwy interchange, Castle Rock 194.31: SH 470/E-470 interchange, Lone Tree 195.13: Enter Arapahoe County 197.18: SH 88 East/Arapahoe Rd interchange, Greenwood Village 199.38: SH 88 West/Belleview Ave interchange, Enter Denver County 200.09: I-225 interchange 201.57: US 285/SH 30/Hampden Ave interchange

204.03: SH 2/Colorado Blvd interchange 207.48: US 85/Santa Fe Dr interchange 207.99: SH 26/Alameda Ave interchange 209.21: US 6/6th Ave interchange 210.31: BL I-70/US 40/US 287/Colfax Ave interchange 213.62: I-70 Exit 274 interchange 214.46: Enter Adams County 215.24: SH 53/58th Ave interchange 216.30: I-76 Exit 5 interchange 217.00: US 36/I-270 Exit 0 interchange 223.04: SH 128/120th Ave interchange, Northglenn 227.34: Enter Broomfield County 227.74: E-470/Northwest Pkwy Exit 46 interchange 228.02: Enter Adams County 229.10: SH 7 interchange, Enter Broomfield County 231.09: Enter Weld County 235.11: SH 52 interchange 240.11: SH 119 interchange, Longmont 243.14: SH 66 interchange 250.24: SH 56 interchange, Berthoud 252.26: SH 60 East interchange, Johnstown 253.19: Enter Larimer County 255.27: SH 402 interchange 257.30: US 34 interchange, Loveland 262.29: SH 392 interchange, Windsor 269.37: SH 14 interchange 277.88: SH 1 interchange, Wellington 291.97: Enter Weld County 298.87: Wyoming border

Annual Average Daily Traffic (2004):

8500 at New Mexico border 14,900 south of Main St, Trinidad 8600 north of BS 25, Aguilar 7500 north of US 160/SH 10, Walsenburg 12,500 north of Walsenburg BL 25 16,800 north of SH 165, Colorado City 34,100 north of SH 45, Pueblo 60,300 north of Abriendo Ave. 71,200 north of 13th St. 28,200 north of US 50/SH 47 27,400 north of Eden 37,400 north of US 85, Fountain 61,900 north of Academy Blvd., south Colorado Springs 83,300 north of south Nevada Ave. 94,200 north of Bijou St. 103,000 north of north Fillmore St 70,100 north of Briargate Pkwy. 53,600 north of SH 105, Monument 52,200 south of Greenland 55,500 south of Wilcox St./Plum Creek Pkwy., Castle Rock

91,600 north of US 85/Founders Pkwy. 86,500 north of Castle Pines Pkwy. 173,000 north of County Line Rd, Centennial 222,000 north of Orchard Rd, Greenwood Village 193,000 north of US 285/SH 30/Hampden Ave., Denver 169,000 north of Downing St 221,000 north of SH 26/Alameda Ave 203,000 north of US 40-287/Colfax Ave. 254,000 north of Park Avenue West * 191,000 north of I-70 234,000 between I-76 and US 36 149,000 north of Thornton Pkwy., Thornton 87,600 north of SH 128/120th Ave. 67,500 north of SH 52 61,400 north of SH 66, Longmont 60,800 north of SH 56 69,800 north of US 34, Loveland 49,600 north of Harmony Rd., Fort Collins 36,700 north of SH 14 18,200 north of SH 1, Wellington 17,000 at Wyoming border

* The busiest stretch of highway in Colorado

Guide:
I-25 starts off in Colorado just north of Raton Pass, descending down Raton Creek Canyon toward Trinidad. I-25 passes right through the middle of town, using an elevated viaduct over streets and railroad tracks. US 160 joins I-25 at Exit 15 on the north edge of town. North from Trinidad, I-25 generally follows the eastern edge of the mountains and foothills, bypassing to the east of Augilar and Walsenburg. Walsenburg features a marked business loop, and US 160 breaks off to head west. As it continues north toward Colorado City, the terrain gets more rolling, but then flattens out again south of Pueblo.

I-25 flies right through the middle of Pueblo, rather than bypassing it.  The strecth south of downtown in the Abriendo Ave. area has a bunch of substandard features, including 50mph curves, bridges with no shoulders, 25mph exits, short accel/decel lanes, etc. At the Indiana Ave. exit I-25 passes the Rocky Mountain Steel Mill. North of downtown at Exit 101, US 50 West/SH 47, I-25 encouters its first SPUI.

North of Pueblo, I-25 picks up Fountain Creek and follows that north along the west sides of Fountain and Security-Widefield toward Colorado Springs. It is also along the east border of Fort Carson. As I-25 comes into Colorado Springs, it generally follows along the west side of Fountain Creek, swinging around the west side of downtown, then hugging the hillside that marks the west side of the Monument Creek valley through the northwest side of town. I-25 has six lanes through Colorado Springs from Circle Drive in the south to North Academy Blvd in the north. It features two elongated diamond interchanges, one at South Nevada/Tejon, the other at North Nevada/Rockrimmon/Corporate.

I-25 follows the broad Monument Valley from Colorado Springs north to Monument, and forms the east border of the Air Force Academy part of the way. Monument is basically being assimilated into the Colorado Springs metro area. North of Monument at County Line Road, I-25 rises up and crests Monument Hill, sometimes referred to as the Palmer Divide. At an elevation of 7352 feet, it is prone to severe winter weather. As a result, CDOT has continuous lighting along a three or so mile stretch of it, very rare in a rural area. At first I didn't know what the lighting was for, but Mike Ramsey dropped me a line clearing things up.

I-25 then goes through rolling terrain past Greenland and Larkspur, and after a long straight stretch along East Plum Creek arrives in Castle Rock. I-25 passes to the west of the main part of town, but the town has spread out to envelop both sides of the freeway. Castle Rock is also where the pressure of traffic from metro Denver starts to be felt. I-25 picks up a third lane each direction at the Wolfensberger Rd interchange. From Castle Rock north to Lincoln Avenue (Exit 193), I-25 climbs and falls over a very hilly portion of Douglas County, eventually coming to Lone Tree.

At Lincoln Avenue, I-25 enters the more developed portion of metro Denver. The highway has five lanes in each direction from Lincoln up to I-225 (Exit 200). Near Orchard Road and Belleview Avenue, I-25 skirts the west side of the Denver Tech Center, a massive office park that chokes I-25 and surrounding roads each rush hour. From I-225 northward I-25 has four lanes in each direction.

The section from I-225 to Santa Fe Drive used to be a substandard, with the worst section in a part called the Narrows, from University Blvd to Logan St (MP 205-206). This area hadn't seen a significant upgrade since it was built in the '50s and it was showing. There was poor drainage and minimal shoulders, and the underpass at Logan St would flood during heavy rains, twice in fact during the summer of 1998. It received the nickname Lake Logan. The underpass at Evans Av also had a habit of flooding. But the Southeast Corridor Project, later renamed to T-REX (Transportation Expasion Project) remedied many things in the area. The $1.6 billion project, from Summer 2001 to Fall 2006, expanded I-25 to four lanes in each direction (up from three) from Broadway to I-225, and five lanes from I-225 to C-470 (up from three). The Regional Transportation District at the same time built its Southeast Line along I-25's west side from the existing Broadway station southeast to Lincoln Avenue. Interchange, bridge, ITS, and drainage improvements were made. The left exit and left entrance at the I-225 interchange were eliminated. The project was possible thanks to state voters in November 1999 approving TRANs and metro RTD residents approving bonding for the light rail. A seperate project that ran almost concurrently was rebuilding the I-25 viaduct over Broadway, which at one time was rated as one of the worst bridges in the state.

From Santa Fe northward, I-25 has four lanes in each direction and stays within earshot of the South Platte River until north of Speer Blvd. The section from 6th Avenue (Exit 209) to 20th Street (Exit 212C) has, I feel, too many closely spaced entrances and exits, as well as a sharp curve going over the South Platte River next to Invesco Field at Mile High.

Five miles from 20th Street to north of US 36 have reversible HOT lanes (high occupancy or toll) in the median, two lanes wide Vehicles with two or more people, motorcycles and alternative fuel vehicles (electric, ethonal, propane) are allowed to use the lanes for free, while single occupant vehicles can use them via an electronic toll. The toll point is just south of 58th Ave with HOVs directed into the west lane and toll vehicles into the east lane where the overhead toll reader is. Toll payers need an ExpressToll account, the same eletronic collection system first used by E-470. The lanes are controlled with changeable message signs and gates, with flow going southbound in the morning and northbound evening and weekends. For northbound traffic, entry points are 1) I-25 near 20th St and 2) 20th St downtown with exit points to 1) 70th Ave, 2) westbound US 36 and 3) northbound I-25 north of US 36.  For southbound traffic entry points are 1) I-25 north of US 36, 2) 70th Ave and 3) eastbound US 36 near Pecos with exit points to 1) southbound I-25 near Speer and 2) 19th St downtown. The toll for single occupant vehicles depends on the time of day, but is highest during peak hours. The idea to make the toll high enough so that the lanes don't get so much traffic that HOVs are delayed.

The interchange with I-70 (Exit 214) is known as the Mousetrap, and is much better off now than it used to be. See the History section below for more. From the Mousetrap up to the Turnpike Tangle, I-25 has four lanes with auxiliary lanes going each direction, and a nice broad concrete cross section. The Turnpike Tangle is my name for the mass of ramps and bridges that make up I-25's two interchanges with I-76 (Exit 216) and I-270/US 36 (Exit 217), along with the I-76/270 interchange. Construction was ongoing from the mid-'90s to 2008, with the goals of extending I-270 from 76 northwest to 25/36, and connecting HOV lanes on 25 and 36 with direct ramps. See my I-270 and US 36 listings for more.

From the Turnpike Tangle north and out of the metro, I-25 has three lanes in each direction. At 104th Avenue, the speed limit goes from 55 to 65, and at SH 128/120th Avenue (Exit 223), a good chunk of the traffic melts away. From 120th up past Wellington, I-25 is mostly straight and flat, with the steepest grade being just south of SH 56/Berthoud (Exit 250). At SH 66 (Exit 243) the three lanes in each direction become two, and it is like that all the way to Wyoming. From SH 7 to Wellington, there are exits, on average, about every three miles, so you keep busy avoiding exiting/entering cars. Traffic levels drop very suddenly at Fort Collins. Heading north, when you hit the Buckeye Road exit (Exit 281), the land suddenly changes from lush, green farmland to brown prairie. Ah, the wonders of irrigation.....

I-25 is the main artery of the North Front Range for traffic between Denver and Fort Collins. There has been an ongoing North Front Range Transportation Alternatives Feasibility Study to determine the best thing to do in the corridor, which could be one or a combination of passenger rail service, intercity bus service, HOV lanes, or more general lanes. Some numbers: There were 88 accidents in the 14-mile stretch from SH 7 to SH 66 in 1992, but that ballooned to 183 in 1996. The scariest part is that traffic counts keep increasing. Planners expect the counts to increase by (not to) 600,000 motorists between Loveland and Denver by 2020. Some call it "a looming transportation nightmare." (April 13, 1998 Fort Collins Coloradoan by the AP) Interchange improvement projects completed since the late '90s include Exit 240 (SH 119) at Longmont, Exit 268 (SH 68) at Fort Collins, Exit 235 (SH 52) at Dacono and Exit 257 (US 34) at Loveland.

• Welcome to Colorful Colorado. State welcome sign on I-25 entering from New Mexico at Raton Pass. (August 2010)
• Different Perspective. Better picture of the sign. Photo by David Hererra. (December 2010)
  
• Raton Pass Scenic Pullout. Northbound just north of the border is a scenic pullout, with this view looking to the north. (August 2010)
  
• Trinidad Business Loop. There is no state-maintained BL in Trinidad. Perhaps it's a locally signed route, and CDOT played along. Photo courtesy Mike Ballard.
• Overhead Signs in Trinidad. Note the SH 12 sign has a Scenic and Historic Byway marker on it. These signs no longer exist due to reconstrution. Photo courtesy Mike Ballard.
• Commercial Street Exit. Northound on the Trinidad viaduct, with barrier on the left side because both directions of traffic were using the northbound side when this picture was taken. (August 2010)
• Trinidad Viaduct and Amtrak Station. A view of the east side of the I-25 viaduct through Trinidad, from the Amtrak platfrom looking toward the Cedar/Nevada intersection. (June 2014)
  
• Southbound Viaduct Reconstruction. The view from SH 12 under I-25 at the southbound viaduct under construction. (August 2010)
  
• Elevated Trinidad Freeway. The 1960s northbound viaduct pre-reconstruction. Photo by Mike Ballard.
• I-25 & US 160 Overlap Markers. Proof the overlap of I-25 and US 160 is marked, here shown just north of Trinidad. (August 2010)
  
• 1990s Version of the Markers. Somewhere north of Trinidad. Photo by Mike Ballard.
• Northbound Walsenburg Exit. Northbound sign bridge at the exit for the Walsenburg business loop. US 160 doesn't technically leave I-25 until the next interchange, but traffic is directed to get off here for Alamosa. (August 2010)
  
• Old Exit 49 Sign. 1990s sign that no longer exists. This has got to be one of the weirdest-looking guide signs I've ever seen. All-caps, "NEXT RIGHT", black around the US marker. Photo courtesy Mike Ballard.
• US 160/SH 10. Northbound I-25 as it's approaching the US 160/SH 10 interchange at Walsenburg, with a heck of a telephoto looking ahead from the top of one crest to another. Photo by Mike Ballard.
• Southbound Walsenburg Exit. Three sign panels piled onto an overhead sign bridge at Exit 52 on the north side of town. (August 2010)
  
• South of Exit 83. The scenery on southbound I-25 south of Exit 83 in Pueblo County. (August 2010)
  
• Stem Beach Interchange. The view from the top of the Stem Beach ramp looking north back toward Pueblo. (May 2004)
  
• Spanish Peaks. Southbound I-25 south of SH 45/Pueblo Blvd., looking all the way to the Spanish Peaks, 65 miles away. (May 2004)
• Pueblo Boulevard Interchange. Northbound I-25 as one approaches the SH 45/Pueblo Blvd interchange on the south side of Pueblo. In the distance you can see the stacks from the Rocky Mountain Steel Mill. Photo by David Herrera. (October 2005)
  
• North of Indiana Avenue. Northbound I-25 at a railroad overpass north of Indiana Ave. in Pueblo. (May 2004)
  
• Approaching Abriendo. Northbound I-25 near Abriendo Avenue. Photo by Mike Ballard.
• Arkansas Bridge. Northound I-25 going up and over the bridge over the Arkansas River in Pueblo. (May 2004)
• View from 8th Street. Looking south down on a curving, tree-lined I-25 from the 8th Street overpass in Pueblo. (May 2004)
  
• US 50 East Interchange. Overhead signs on a very wide overhead sign structure at the US 50 East interchange in Pueblo. (May 2004)
  
• Southbound at 29th Street. Soutbound I-25 at 29th Street in Pueblo, featuring an unusual overhead sign with two arrows. (May 2004)
• US 50/SH 47 SPUI. On the southbound offramp at Exit 101 in Pueblo, these are the overhead signs as one approaches the SPUI intersection. (May 2009)
• Median Distance Sign. Nicely-done interchange sequence sign in the southbound median approaching Exit 101. (May 2009)
  
• Exit 101 3/4 Mile. Southbound sign announcing the US 50 West/SH 47 interchange. (May 2009)
• SH 16 Exit First Ramp and Second Ramp. Southbound at SH 16 (Exit 132) in Fountain, showing the signs for the two separate ramps. (May 2009)
  
• At Bijou Street. Northbound I-25 at the Bijou Street underpass in Colorado Springs. Photo by Russell Kroll. (May 2003)
• Near Uintah Street. Shot looking north on I-25 from a pedestrain overpass looking toward Uintah Street. (September 2003)
• Fillmore Street Double Clearance. A shot of the underside of the Fillmore Street underpass on northbound I-25 in Colorado Springs. It appears that the Fillmore underpass was built as two separate bridges (first the northside, then a while later the south side), as evidenced by these two clearance signs. Photo by Russell Kroll. (May 2003)
• Garden of the Gods SPUI. A view of the SPUI at I-25 and Garden of the Gods Road in Colorado Springs as seen sitting at the light waiting to turn left from westbound GOTG to southbound I-25. Photo courtesy David Herrera. (August 2003)
• Nevada/Corporate/Rockrimmon. The southbound overhead sign at the Exit 140 split diamond (post-COSMIX) which features three lines on it, not something you see every day. (February 2008)
  
• Pikes Peak and Academy Boulevard. A view of Colorado's most famous summit while on southbound I-25 in the Academy Boulevard interchange (Exit 150). Photo by David Herrera. (March 2004)
• Monument Hill. Looking south on I-25 from County Line Road at the summit of Monument Hill. In the top right of the photo are two things sticking up which are cell phone towers disguised as trees. (September 2003)
• Rural Lighting North of Monument. Northbound I-25 just north of the County Line Road interchange (Exit 163). This is in the rural section that has lighting due to the possibility of severe winter weather. Photo by Mike Ballard.
• Milepost 169.5. A shot on northbound I-25 near Larkspur of milepost 169.5. Photo courtesy David Herrera. (July 2003)
• Larkspur Exit & Butte. Southbound I-25 at the Larkspur exit (Exit 173). In this stretch you're pointed right at Larkspur Butte. Photo by David Herrera. (October 2005)
  
• South Metro Distance Sign. Northbound I-25 in the south metro. This is a distance sign on a pole in the median. You can see how CDOT marks E-470 as a tollway. Photo courtesy Mike Ballard.
• 470 Exit Sign. And here is what you see when you get nearer. Note the blank line; it now says "Limon" since E-470 was completed up to I-70. Photo courtesy Mike Ballard.
• I-25/470 Stack Interchange. Northbound approaching the Exit 194 interchange. The exit has already gone off to the right. Exit 194 is one of those fully directional, four-level "stack" interchanges. The exit off in the distance is Exit 195, County Line Road. Photo courtesy Mike Ballard. Here's another view of the interchange, taken by me heading west on E-470 in May 1999.
• Arapahoe Station Pedestrian Bridge. View of the pedestrian bridge across I-25 at the Arapahoe light rail station, as seen from the Yosemite St overpass, looking north. (September 2010)
• The Tech Center Runway, 12 Lanes Wide. I-25 in Greenwood Village as viewed looking north from the Orchard station ped bridge in the Tech Center. In the distance is the Belleview Ave exit. I call this section of I-25 "The Runway" because it's wide, straight, fast and lit up like a Christmas tree at night. (Septemer 2010)
  
• I-25/Belleview Overhead Signs. Old button copy overhead signs northbound in Greenwood Village. These signs no longer exist. Photo by Mike Ballard.
• I-25/225 From Union. A look at the Full House undergoing T-REX construction facing north from the Union Avenue overpass. (March 2002)
• I-25/225 From Quincy. The Full House again, north facing south from the Quincy Avenue overpass. (March 2002)
• T-REX Sign. One of T-REX's large project signs, located on southbound I-25 at I-225. (March 2002)
• Yale Avenue Bridge. A shot of the bridge that takes I-25 over Yale Avenue in south Denver. According to Michael McMullen, it was a high performance concrete demonstration project, resulting in one of the most slender prestressed concrete girder bridges in the country. It has served as a prototype for a number of the more slender bridges of this type in Colorado, allowing longer spans or greater vertical clearance. The bridge was built extra wide and as a result no widening or replacement was required on it for the T-REX project. Photo by Greg Gargan, via Michael McMullen.
• I-25/Evans Ramp Meter. Ramp meter on the northbound onramp at Evans Avenue in Denver. This ramp has completely changed due to T-REX construction. (June 2000)
• I-25 Northwest of University Boulevard, Looking Northbound and Looking Southbound. These two pictures were taken from the top of the RTD University Park-n-Ride garage. The northbound picture looks out over the light rail station and into the mouth of the Narrows toward the Franklin Street bridge. The southbound picture looks due east through the University interchange. (August 2006)
  
• I-25 Narrows, Pre T-REX. This was how "The Narrows" section of I-25 looked in south Denver before T-REX reconstruction, looking north from the Louisiana Ave. overpass. This was an extremely substandard section of I-25, due to the fact no serious upgrade had ever been made to the original Valley Highway through here. (January 1999)
• Half Logan Bridge. An interesting site for a couple weeks in Denver. As part of T-REX the Logan Street overpass was being demolished, but weather forced suspension while they were only halfway done. This was the result. (March 2003)
• Alameda Underpass. Northbound on I-25 going under Alameda Avenue. (March 2007)
  
• I-25/6th/8th Overhead Signs. Three signs piled onto an overhead structure northbound approaching 6th Avenue in Denver. Photo by Mike Ballard.
• I-25 Near 8th Avenue, Invesco Field at Mile High. Northbound I-25 in Denver between the 6th and Colfax Avenues exits. The picture provides a pretty good overall view of I-25 in this area. Directly ahead is Invesco Field at Mile High, visible through Xcel Energy's Zuni generating station. Photo by David Herrera. (October 2005)
  
• Ramp Within Colfax Interchange. On the ramp from westbound Colfax Avenue to southbound I-25. The two-lane ramp on the left side is from Auraria Parkway, while on the top of the retaining wall to the right is the ramp from eastbound Colfax. Photo by David Herrera. (July 2003)
• I-25 South Platte River Bridge Picture 1 & Picture 2. These two pictures are of the bridge that takes I-25 over the South Platte River just north of Colfax Avenue in Denver. The first picture is looking north along the river, the second south. Driving along I-25 you would never know this huge structure is here. I didn't realize it was such a large structure until I went biking along the South Platte Trail one Saturday morning. Even these pictures can't really convey how impressive the structure is up close. (June 2001)
• HOV Variable Message Sign. Northbound I-25 approaching the 20th Street exit (212C) in Denver. Over on the right side of the gantry is the exit sign for 20th St., while the thing on the left is the VMS for the upcoming left exit to the HOV lanes. The VMS displays the status of the HOV lanes. (May 1999)
• Park Avenue West Flyover. This is looking north along Park Avenue West with I-25 going across the top of the picture. The long flyover is the Park Ave. West Flyover, open November 1998, which takes traffic from both directions of I-70 and southbound I-25 directly onto Park Ave. West and into downtown Denver. Previously, one had to go through four signals just to get from I-25 to Park Ave. and to downtown. The flyover is expected to save travelers up to 10 minutes during peak drive times. This bridge contains the longest, heaviest girder ever placed by CDOT; two high-capacity cranes had to be brought into Colorado special for this job. Original picture � Colorado Department of Transportation, from the November/December 1998 issue of Milestones, CDOT's bimonthly newsletter.
• I-25/38th Avenue Braid Structure. In the maze of C-D roads along I-25 south of I-70, this structure carries SB I-25 to Park Avenue over SB I-25 to 38th Avenue. According to Michael McMullen, the structure is only 21" thick (which is pretty thin) but is able to span about 134' by using a trick related to the severe skew and load paths. Photo courtesy Michael McMullen.
• I-25 at 44th Avenue. Note to self: Don't try to take pictures through black chain-link fences in the future. This is looking south from the 44th Ave. overpass in north Denver. The reason I ended up with this picture is because there is no other good place to get a picture of the HOV lanes on I-25. They are the two separated lanes in the center, and at this time (noon Saturday) they are going northbound. The separated lanes on the far right are taking traffic from both directions of I-70 south to Park Ave., 38th Ave., or southbound I-25, while the separated lanes on the far left are taking traffic from Park Ave., 38th Ave., and northbound I-25 to both directions of I-70. (January 1999)
• Exit to I-70. Northbound I-25 at the exit to the I-70 C-D road. Off to the right is the ramp to Park Avenue West/38th Avenue peeling off. Photo by David Herrera. (July 2003)
• NB I-25 at US 36. Northbound I-25 approaching the US 36 exit in north Denver (duh!). This is actually the second set of these signs. There are another set about a quarter mile previous. (May 2001)
• Ramp from I-76 Eastbound. Typical weekday congestion on the long ramp from eastbound I-76 to northbound I-25. The ramp merges with mainline I-25, which off to the left, just ahead. Photo by David Herrera. (July 2003)
• I-25/SH 119 Construction. Photo on westbound SH 119 approaching a new I-25 overpass being built during an interchange upgrade project. The bridge directly ahead with the equipment on it is the new northbound I-25 bridge. The old bridges are in the distance. Compare the width of the new and old underpasses. The new ramps are directly behind the picture. (July 1998)
• Little Thompson Valley. Northbound approaching the Berthoud SH 56 exit is a long downhill grade as I-25 falls into the valley for the Little Thompson River. I-25 is visible climbing up the other side of the valley as is the odd kink to the left I-25 has as it goes through the SH 56 interchange. (October 2010)
  
• I-25 Near Windsor. Just your typical weekday afternoon on southbound I-25 north of the Windsor exit. (July 1998)

History:
Before I-25 was constructed, US 87 pretty much exactly followed its alignment. As a consequence, US 87 is not signed and basically nonexistent. Outside of Denver, the freeway that would become I-25 started as scattered expressway and freeway sections of US 85-87 and US 87-SH 185. See those listings for more. I-25 first appears on state maps in 1961.

• Circle Drive (former SH 29)/US 24 East: Widening to six lanes.
• South Nevada/Tejon: Total interchange rebuild to eliminate sharp ramps and confusing turns. Completed 2004.
• Bijou to Fillmore: Widening to six lanes. Completed 2000.
  
• Woodmen Road: Interchange rebuild. Completed 2004.
• North Academy: Eliminating two of the loops in the interchange. Completed 1998.

The Valley Highway: What was originally built in Denver was not I-25, but the Valley Highway. It was completed in sections from north to south. All 11mi of the entire route (from 58th Ave. to Evans Ave.) opened for traffic on November 23, 1958. It was only built to four lanes, and traffic quickly reached capacity. Contingencies were built into the right-of-way for six lanes, but CDH could not afford to build all six. Funding would have come from the Interstate system for it, since the Valley Highway would eventually be I-25, but the funding was not available until 1957, too soon to be used for the Valley Highway.

The Mousetrap: The Mousetrap is what the I-25-70 interchange in north Denver is called. The original Mousetrap was an interchange on the Valley Highway, not designed or built to ever be an Interstate. It opened in 1951 when the first 2.2-mile section of the Valley Highway opened from 38th to 52nd Avenues. The Mousetrap was the interchange with 46th Avenue, at the time a major east-west street. The Mousetrap cost $2.2M, the largest contract ever awarded by CDH.

In the 1960s, I-70 was slated to be extended across Colorado, rather than just ending in Denver, so I-70 opened in 1964 as an elevated highway over 46th Avenue. The old Valley Highway interchange at 46th then became the link between I-25 and I-70. It still had substandard ramps and curves, and accidents were "common". The Mousetrap name dates from the late 1960s when airborne traffic reporter Don Martin observed the intertwining ramps could trap a mouse. In 1993 Martin remarked, "It had a terrible curve so that eastbound trucks going from I-25 to I-70 were always rolling over. They were the mice."

In 1971 the Denver Police Department built a 60-foot observation tower in the middle of the Mousetrap to watch for accidents and monitor traffic conditions. The substandard Mousetrap remained for over 20 years, when in 1984 it snagged its ultimate victim: Before dawn on August 1, 1984, a truck carrying six armed Navy torpedoes overturned on the SB-EB ramp. Both freeways were closed for eight hours so the torpedoes could be cleared, resulting in a traffic nightmare. The accident became a national news event and made Congress aware of Denver's problems with the Mousetrap. It was the pivotal event in starting reconstruction of the Mousetrap. At the time, the interchange carried 300,000 vehicles a day; 1997's count was 340,000 VPD, more than projected to use it in 2010.

Construction on rebuilding the Mousetrap started in June 1987. Many phases followed, including: New 44th Avenue bridge; new I-25 alignment through interchange; new I-70 alignment through interchange; widen I-25 from 38th to 58th Avenues and new HOV lanes; reconstruct 58th interchange; reconstruct 38th/Park interchange including huge flyover into downtown; rebuild I-70 from I-25 to Washington; and rebuild I-70 from Washington to Brighton. $269M later, the reconstruction was finished with a dedication of the westbound I-70 viaduct on December 16, 2003.
Info from articles in the March 23, 1998 and December 16, 2003 Rocky Mountain News

The Mousetrap in 1958, looking north.

Looking south along I-25 over the Mousetrap in 1998. HOV lanes go down the middle. Both graphics are from the March 23, 1998 Rocky Mountain News.

Related Site: I-25 @ Interstate Guide

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Last updated 8 November 2014