Alternatives

Draft Project Alternatives

Alternatives are different conceptual engineering designs that seek to improve the Speer Boulevard and 23rd Avenue bridges and interchanges. A wide range of potential solutions were evaluated and refined to nine draft alternatives, including a No Action alternative.

These alternatives will go through two rounds of evaluation called "alternatives screening". The first round evaluates the alternatives against the Purpose & Need. Any alternative that does not meet the Purpose & Need will not be considered further. In the second round of evaluation, the remaining alternatives will be evaluated against more detailed criteria and compared against each other. The final alternative(s) and the No Action alternative will be carried forward into the NEPA process.

Bike & Pedestrian Facilities

Because of the draft Purpose & Need for this study, all draft alternatives will include bike and pedestrian facilities on both sides of the Speer Boulevard and 23rd Avenue crossings of I-25 to connect to local networks. These facilities will be shown in refinements to the alternatives and included in the early 2025 public meeting.

The draft alternatives include:

One alternative for No Action
Three alternatives for 23rd Avenue
Five alternatives for Speer Boulevard

Review each of the draft alternatives, noting the design, signalized and unsignalized crossings, safety, and other considerations listed for each alternative.

No Action Alternative

With the No Action alternative, no improvements would be made other than routine maintenance. This alternative would maintain the existing Speer Boulevard and 23rd Avenue bridges over I-25, and their interchanges with I-25.

Proposed Alternative No Action Map — Map of the existing I-25: Speer Boulevard and 23rd Avenue Bridge interchange. Project area is along Interstate 25 from 23rd Avenue in the south, to 15th Street in the north, and includes the adjacent areas along Speer Boulevard and Water and Platte Streets. Map legend identifies four existing unsignalized pedestrian crossings at the Speer Boulevard ramps – two on either side of I-25; and three at the 23rd Avenue ramps from east of I-25. Map also identifies one existing signalized intersection at the Speer Boulevard ramps to west of I-25, and one at the 23rd Avenue ramps from west of I-25. Additional callouts identify the locations of the existing bridges at Speer Boulevard and 23rd Avenue, crossing over I-25.

23rd Avenue Alternatives

These three alternatives provide adequate vertical clearance for vehicles on l-25 and improve maintenance and structural integrity of the 23rd Avenue bridge over I-25, as well as improve bike and pedestrian connections. Sidewalks will be Installed on both sides of 23rd Avenue in all the alternatives and existing bike facilities will be maintained.

23rd Avenue Braid Alternative

A weave occurs when vehicles are both entering and exiting the interstate in the same lane, creating unsafe conditions. A braid eliminates this weave by having exiting and entering traffic cross over or under each other.

This alternative has northbound vehicles exiting I-25 to go under 23rd Avenue to get to Speer Boulevard. Those who want to get on and off of I-25 to 23rd Avenue will exit on more traditional ramps. This removes the existing weave for drivers going north on I-25 from 23rd Avenue and those trying to get off of I-25 to Speer Boulevard.

A signal would be added to the east side of the 23rd Avenue bridge to improve non-motorist safety.

Proposed Alternative 23rd Avenue Braid — Map rendering of the 23rd Avenue Braid Alternative. This alternative demonstrates northbound vehicles exiting I-25 to go under 23rd Avenue to get to Speer Boulevard. This eliminates Speer bound exiting traffic and weaving with northbound I-25 traffic from 23rd Avenue in the same lane. A signalized intersection would be added to the east side of the 23rd Avenue bridge giving two signalized intersections on the 23rd Avenue ramps – one on each side of I-25. Additional call-out identifies the location of the existing bridge at 23rd Avenue crossing over I-25.

Close 23rd Avenue Interchange with I-25 Alternative

The Close 23rd Avenue Interchange with I-25 Alternative removes the existing ramps to get off and on I-25, so there will not be access to or from I-25 at 23rd Avenue.

Closing the ramps at 23rd Avenue would eliminate the weave on I-25 between 23rd Avenue and Speer Boulevard. This allows 23rd Avenue to serve bikes and pedestrians.

Visitors to businesses, such as the Children’s Museum, Aquarium, and REI will need to use Speer Boulevard or other roads. Access to 17th Avenue to, and from, I-25 will still be available.

Close 23rd Avenue Interchange with I-25 Proposed Alternative — Map of the Close 23rd Avenue Interchange with I-25 Alternative. This alternative removes the existing ramps between I-25 and 23rd Avenue, eliminating the northbound weave between 23rd Avenue and Speer Boulevard east of I-25. Map also identifies the existing bridge at 23rd Avenue.

23rd Avenue Bridge Replacement Only Alternative

The 23rd Avenue Bridge Replacement Only Alternative replaces the bridge and ramps and installs a new signal on the east side at the ramps.

This alternative does not improve the short northbound I-25 weave between the 23rd Avenue on-ramp and the eastbound Speer Avenue Boulevard off-ramp.

This alternative provides improved safety for non-motorized users by adding a signal on the east side of the 23rd Avenue bridge. This will improve non-motorist safety by removing the “free-flow” ramp movements.

Access to and from I-25 from 23rd Avenue would remain.

Proposed Alternative of 23rd Avenue Bridge Replacement Only Map — Map of the 23rd Avenue, Bridge Only, Alternative. This alternative replaces the bridge and ramps on the east side of I-25 at 23rd Avenue; however, the northbound Speer Boulevard offramp traffic would still merge with 23rd Avenue traffic accessing northbound I-25. A signalized intersection would be added to the east side of the 23rd Avenue bridge giving two signalized intersections on the 23rd Avenue ramps — one on each side of I-25. Additional call-out identifies the location of the existing bridge at 23rd Avenue crossing over I-25.

Speer Boulevard Alternatives

The five Speer Boulevard alternatives provide adequate vertical clearance for vehicles on I-25 and improve maintenance/structural integrity of the Speer Boulevard bridges over I-25, as well as improve pedestrian, bicycle, and non-motorist connections. Bike and Pedestrian facilities will be installed on both sides of Speer Boulevard, in all the alternatives. Also, all Speer Boulevard alternatives remove the weave between the I-25 northbound on- and off-ramps, improving safety for vehicles on I-25.

Speer Boulevard Bridges Replacement Only Alternative

The Speer Boulevard Bridges Replacement Only alternative would increase the vertical clearance over I-25 with new bridges and ramps that have the same layout as what exists today.

The loop ramp in the northeast corner of the interchange will be removed to eliminate the existing weave for those getting on and off I-25 at Speer Boulevard, in the northbound direction. In this alternative, northbound I-25 traffic exiting westbound Speer Boulevard would exit before the Speer Boulevard bridge and make a left-turn at the top of the ramp where there will be a new traffic signal.

This alternative would improve bike and pedestrian safety by adding a traffic signal on the east side of the interchange. A traffic signal will provide a pedestrian signal for bikes and pedestrians. This allows for a protected crossing of the ramps for bikes and pedestrians.

Proposed Alternative Speer Boulevard Bridges Replacement Only — Map of the Speer Boulevard, Bridges Only, Alternative. This alternative would have the same ramp layout that is currently in-place except that the loop ramp in the northeast corner of the interchange would be removed to eliminate the existing weave for vehicles entering and exiting I-25 at Speer Boulevard in the northbound direction. I-25 traffic exiting to access westbound Speer Boulevard would exit before the Speer Boulevard bridge and make a left-turn at the top of the ramp where a new signalized intersection would be added, giving two signalized intersections on the 23rd Avenue ramps; one on each side of I-25. Additional call-out identifies the location of the existing bridge at 23rd Avenue crossing over I-25.

Speer Boulevard Single-Point Urban Interchange with I-25 Alternative

The Speer Boulevard Single-Point Urban Interchange with I-25 alternative has a single traffic signal in the middle of the bridge. The left turns all occur at that single traffic signal, while right turns are more traditional to get on and off of I-25.

This alternative provides improved vehicular operations by having the traffic go through one signal.

This alternative would improve bike and pedestrian safety by adding a traffic signal to the Speer Boulevard bridge. A traffic signal will provide a pedestrian signal for bikes and pedestrians. This allows for a protected crossing of the ramps for bikes and pedestrians.

Proposed Alternative Speer Boulevard Single-Point Urban Interchange with I-25 — Map of the Speer Boulevard, Single-Point Interchange with I-25 Alternative. This alternative has a single traffic signal in the middle of the bridge, with all left turns occurring at this location. North and southbound traffic exiting I-25 would flow either to Speer Boulevard east or west. East and westbound Speer Boulevard traffic can access ramps to I-25 north or south or continue on Speer. Map identifies one signalized intersection at the existing bridge at Speer Boulevard crossing over I-25.

Speer Boulevard Diamond Interchange with I-25 Alternative

The Speer Boulevard Diamond Interchange with I-25 alternative is a traditional interchange type with I-25 where left and right turns occur at a new traffic signal at both ends of the bridge.

This alternative improves bike and pedestrian safety by adding a traffic signal on the east side of the interchange and a more traditional interchange for motorists.

Proposed Interchange Speer Boulevard Diamond Interchange with I-25 — Map of the Speer Boulevard Interchange with I-25 Alternative. This alternative is a traditional diamond interchange, where left and right turns occur at a new traffic signal at both ends of the bridge. Map identifies two signalized intersections at the Speer Boulevard ramps, one on each side of I-25 and the location of the existing bridge at Speer Boulevard crossing over I-25.

Speer Boulevard Partial Clover Leaf Interchange with I-25 Alternative

The Speer Boulevard Partial Clover Leaf Interchange with I-25 alternative operates like a traditional interchange with ramps starting and ending at traffic signals at each end of the Speer Boulevard bridge.

For those traveling south on I-25 to go east or west on Speer Boulevard, drivers will use a loop ramp in the southwest corner.

This alternative improves bike and pedestrian safety by adding a traffic signal on the east side of the interchange. Bikes and pedestrians would need to cross multiple lanes of traffic in the southwest corner of the interchange

Proposed Alternative Speer Boulevard Partial Clover Leaf Interchange with I-25 — Map of the Speer Boulevard Partial Clover Leaf Interchange with I-25 Alternative. This alternative operates like a traditional diamond interchange, where left and right turns occur at a new traffic signal at both ends of the bridge, except for the southbound I-25 exiting traffic. Vehicles traveling south on I-25 to access Speer Boulevard, either east or west, would continue under the Speer Boulevard bridge and then use a cloverleaf loop ramp in the southwest corner of the interchange. Map identifies two signalized intersections at the Speer Boulevard ramps, one on each side of I-25 and the location of the existing bridge at Speer Boulevard crossing over I-25.

Speer Boulevard Diverging Diamond Interchange with I-25 Alternative

In the Speer Boulevard Diverging Diamond alternative, eastbound and westbound traffic on Speer Boulevard will “cross over” each other to travel across the bridge on the left-side of the road (opposite the normal right-side driving). The cross over will occur at both sides of the bridge at traffic signals. An example of this can be found at U.S. 36 and McCaslin Boulevard.

This design eliminates the need for traditional left-turns at the traffic signals, which improves vehicle operations and safety.

This option could allow for separated bike and pedestrian facilities through the center of the bridge and would improve bike and pedestrian safety by removing left turn conflicts with traveling vehicles

Proposed Alternative Speer Boulevard Diverging Diamond Interchange with I-25 — Map of the Speer Boulevard Diverging Diamond Interchange with I-25 Alternative. This alternative shows eastbound and westbound traffic on Speer Boulevard “cross over” each other to travel across the bridge on the left side of the road. The cross-over will occur at both sides of the bridge at traffic signals. The crossing allows for vehicles to turn left on and off freeway ramps more efficiently without stopping or crossing opposing lanes of traffic. Map identifies two signalized intersections at the Speer Boulevard ramps, one on each side of I-25 and the location of the existing bridge at Speer Boulevard crossing over I-25.