CDOT Unveils Concepts for Speer and 23rd Avenue Bridges over Interstate 25

By Allen Cowgill

A pedestrian, person on a scooter, and cars take the West 23rd Avenue bridge over I-25. CDOT hopes to replace this bridge and has begun sharing concepts with the community. Photo by Allen Cowgill

In April, the Colorado Department of Transportation (CDOT) unveiled potential concepts for bridges over Interstate 25 at West 23rd Avenue and at Speer Boulevard. 

The project has been in the works since 2021 as part of the broader 2017 study on what the future holds for the Central Denver segment of I-25. The two bridges, constructed in the 1950s, are nearing the ends of their useful lives. 

The bridges have also been struck numerous times by trucks due to their clearances, among the lowest along all of I-25. CDOT standard clearance for bridges is 16 feet 6 inches. At the lowest point, clearance for these bridges is 12 feet 5 inches.

In addition to bringing the bridges up to clearance standards, CDOT would like to improve safety and better accommodate pedestrians, bicycles and other micromobility devices such as e-bikes and electric scooters on the bridges. For example, today the West 23rd Avenue bridge has a substandard, narrow sidewalk on one side and no paved sidewalk on the other.

CDOT presented five options for a new Speer Boulevard bridge at a community open house in April, while also leaving the door open for a “no-action alternative,” where current bridges would continue to be maintained as best they can.

Speer Boulevard bridge replacement options include:

  1. Replacement only: Replacing the bridge, removing the current loop ramp exit on the northeast corner of the interchange and adding a stop light on the eastern end of the interchange. 
  2. Single-point urban interchange: This option has a single traffic signal in the middle of the bridge where all the intersection’s left turns occur, with right turns in more traditional locations on either side of the bridge.
  3. Diamond interchange: A more traditional interchange with traffic signals on either side of the bridge and off-ramps in all directions.
  4. Partial cloverleaf interchange: Would add a cloverleaf ramp on the southwest corner of the intersection and remove the cloverleafs on the eastern side of the intersection, with traffic signals on either side of the bridge.
  5. Diverging diamond interchange: Similar to the interchange at U.S. 36 and McCaslin Boulevard in Superior, this design eliminates left-turn conflicts by having traffic cross over to the opposite side of the bridge (left-hand side).

Options for replacing the West 23rd Avenue bridge include:

  1. Braided weave: Creates a braid where traffic exiting northbound I-25 to Speer Boulevard goes underneath the on-ramp for 23rd Avenue traffic going north onto I-25. An additional traffic signal is added to the eastern side of the bridge.
  2. Close the interchange: Closing the ramp would eliminate the weave conflict between northbound 23rd Avenue traffic entering on I-25 and traffic exiting I-25 to Speer Boulevard. It would also allow Jefferson Park to be better connected to the Central Platte Valley for pedestrians, wheelchair users, and people who bike and use scooters. Visitors to businesses such as the Children’s Museum, Aquarium and REI would need to use the Speer Boulevard, 20th Avenue or 17th Avenue exits, adding three to four minutes of travel time. 
  3. Bridge replacement only: This option replaces the bridge and adds a traffic signal on the eastern side of the intersection to eliminate the current free-flow traffic movements and increase safety on the eastern side of the bridge.

Initial concepts for both bridges showed options for vehicles. Later this summer, CDOT will host a community meeting to present options recommended for advancing to the next stage of the process. These concepts will incorporate bike and pedestrian options. 

Later this year and throughout 2025, CDOT will move into the environmental compliance phase of the project. If the project is given the green light to move forward, final designs and construction options will be studied in 2026.

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