Iris Avenue Transportation Improvements Project

Iris Avenue is a key city street for all types of travel because it provides one of the only direct east-west connections in North Boulder.

It is also a high-risk street for crashes and feels unsafe for people who walk, bike, drive and take the bus in our community.

Prioritizing Iris Avenue improvements for all travelers offers our community the largest safety and connectivity benefits.

In Detail: Why improve Iris Avenue?

City plans, federal guidance and community input call for proactive safety improvements to make Iris Avenue safer, and more comfortable and connected for everyone, no matter how you travel:

• Iris Avenue is the second of three corridors prioritized for improvements in the city’s Core Arterial Network (CAN) initiative.
  • The CAN is Boulder’s connected system of multimodal transportation — taking the bus, driving, biking and walking — improvements along Boulder’s main corridors that will help reduce the potential for severe crashes and make it more comfortable and convenient for people to get where they need to go along Boulder’s main corridors.
• Iris Avenue is on the city's High Risk Network.
  • The 2023-2027 Vision Zero Action Plan identified Iris Avenue from 19th to 28th streets as part of the High Risk Network (HRN), where nearly half of all fatal and serious injury crashes occur, or are likely to occur in the future, despite comprising only a small part – just 7% – of city streets. The HRN identifies this section of Iris Avenue as having five of the six risk factors that account for the most frequent and severe crashes.
• Iris Avenue is part of the Low Stress Walk and Bike Network.
  • The city's 2019 Low Stress Walk and Bike Network Plan recommends protected bike lanes for Iris Avenue and creating more space between vehicle lanes and people walking.
• Our community feels unsafe on Iris Avenue.
  • Through community engagement, we've heard from hundreds of community members that Iris Avenue feels unsafe regardless of mode of travel, vehicle speeding is an issue and the street is noisy and uncomfortable.

The core study area extends east and west on Iris Avenue from Broadway to 28th Street. The secondary study area extends north and south of Iris Avenue, from roughly Norwood Avenue to the north and Balsam Avenue/Edgewood Drive to the south. The city is evaluating improvements such as traffic calming on nearby streets as a concurrent project.

Iris Avenue is a key city street for all types of travel because it provides one of the only direct east-west connections in North Boulder. It is also a high-risk street for crashes and feels unsafe for people who walk, bike, drive and take the bus in our community. Prioritizing Iris Avenue improvements for all travelers offers our community the largest safety and connectivity benefits.

In Detail: Why improve Iris Avenue?

City plans, federal guidance and community input call for proactive safety improvements to make Iris Avenue safer, and more comfortable and connected for everyone, no matter how you travel:

• Iris Avenue is the second of three corridors prioritized for improvements in the city’s Core Arterial Network (CAN) initiative.
  • The CAN is Boulder’s connected system of multimodal transportation — taking the bus, driving, biking and walking — improvements along Boulder’s main corridors that will help reduce the potential for severe crashes and make it more comfortable and convenient for people to get where they need to go to create safe, comfortable connections along Boulder’s main corridors.
• Iris Avenue is on the city's High Risk Network.
  • The 2023-2027 Vision Zero Action Plan identified Iris Avenue from 19th to 28th streets as part of the High Risk Network (HRN), where nearly half of all fatal and serious injury crashes occur, or are likely to occur in the future, despite comprising only a small part – just 7% – of city streets. The HRN identifies this section of Iris Avenue as having five of the six risk factors that account for the most frequent and severe crashes.
• Iris Avenue is part of the Low-Stress Walk and Bike Network.
  • The city's 2019 Low-Stress Walk and Bike Network Plan recommends protected bike lanes for Iris Avenue and creating more space between vehicle lanes and people walking.
• Our community feels unsafe on Iris Avenue.
  • Through community engagement, we've heard from hundreds of community members that Iris Avenue feels unsafe regardless of mode of travel, vehicle speeding is an issue and the street is noisy and uncomfortable.

Each alternative has trade-offs and competing priorities. Alternative B best balances community priorities, advances city policies and implements industry best practice safety improvements. Its benefits respond to the highest community priorities for crash reduction, moderating vehicle speeds, providing bike and pedestrian comfort and preserving trees, with minimal added travel time. The recommendation:

• Reconfigures vehicle lanes (between 13th Street and Folsom/26th Street) to achieve the most safety benefits like moderating vehicle speeds and reducing crashes and crash severity with minimal added travel time.
• Doesn’t widen the roadway, which means it costs less, reduces adjacent property impacts, and takes less time to implement.
• Includes a center turn lane to reduce common vehicle crash types, supports vehicles turning in and out of side streets and driveways, and provides dedicated space for day-to-day emergency response.
• Includes a two-way protected bike facility that supports people of all ages and abilities, disaster emergency response, and year-round maintenance.
• Preserves the existing public street trees.
• Includes protected intersections, which provide safer crossings and reduce common crash types: right-turn crashes and pedestrians/bicyclists crossing the street.
• Makes changes to signals to separate turning vehicles from people walking and biking at major intersections, which has greater safety benefits for people biking, and smaller vehicle travel time impacts than one-way protected bike lanes.

In Detail: What are the recommended improvements?

View details in the Conceptual Design Tour on the Virtual Open House.

Traffic modeling and analysis determined the Iris Avenue “bookends” are key to moving people and providing travel time reliability for all who travel the corridor. While there will be multimodal safety improvements, the vehicle lane configuration will not change in order to balance community priorities of improving safety for all while keeping everyone moving. The bookends:

• Maintain current vehicle lane configuration to preserve travel time reliability for all who travel along the corridor.
• Include two-way protected bike lanes that continue from end-to-end.
• Optimize existing crossings and connections to key destinations.
• Provides access management at commercial driveways to reduce recurring crashes.

In Detail: What are the bookend improvements?

View details in the Conceptual Design Tour on the Virtual Open House.

The recommendation prioritizes important safety improvements with minimal changes to travel time for all users. Today, the average end-to-end travel time is between 3 and 4 minutes and the slowest trips can take between 4 and 5 minutes. Currently, most people driving on Iris Avenue speed to shorten their travel time at the cost of the community’s safety.

Traffic modeling shows the travel time for the average trip increases by 3 to 46 seconds, most trips increase by 2 to 58 seconds, and the slowest trips increase by 1 second to 2 minutes 09 seconds. In general, travel time increases of around 40-60 seconds or less are mostly imperceptible changes a driver wouldn’t feel over time.

Though the posted speed limit on Iris is 35 mph, most people are driving over the speed limit – at 40 and 45 mph or more. Speed increases the risk of serious injury or death: a pedestrian has a 47% chance of dying when hit by a vehicle driving the speeds seen on Iris.

The recommendation moderates vehicle speeds and reduces the number and severity of crashes. Redesigning the road addresses the common crash types on Iris (rear-end, left-turn and right-angle crashes) and responds to community priorities for crash and vehicle speed reduction.

Safety is a priority for the city. The recommendation includes a center turning lane and a two-way bike lane that can both be used as an emergency vehicle lane or an evacuation lane during emergencies.

The graphics below highlight how the street will be used during day-to-day emergency and disaster response scenarios.

Day-to-day emergency response and disaster emergency response are two of several key considerations for the project. Design development was informed by the city’s Boulder-Fire Rescue and Police departments, and the Office of Disaster Management (ODM) for the City of Boulder and Boulder County.

We will continue to work closely with our public safety partners throughout the design process.

An evaluation of the recommendation showed that it will not affect air quality and the environment, including nearby streams and soil. The recommendation also preserves 92% of the existing public street trees, removing only 10-12 of our 150 public street trees on Iris Avenue.

In Detail: What about the climate?

Tree Canopy

Maintaining our tree canopy is a key part of our community’s sustainability and climate action goals. The community also shared that they want placemaking and attractive facilities – and public street trees are key to these goals. The City of Boulder Urban Forestry Strategic Plan and Boulder Valley Comprehensive Plan (BVCP) recognize the importance of the urban canopy, street trees and streetscapes, and the importance of the urban forest. There are currently 150 public street trees along the Iris Avenue project area. These trees provide the project area with 25% canopy cover. The citywide overall canopy cover is 16%.

Alternative B does not require roadway widening and so only removes trees to improve sightlines or provide clear space around existing or new sidewalks and bike lanes. Alternative B has minimal impacts to existing public street trees: it will remove 10-12 trees of the existing 150 trees, or about 8% of total tree canopy on Iris Avenue, for sidewalk improvements and sightlines.

Emissions

The evaluation also measures the potential short and long-term impacts to air quality from mobile sources, like vehicle trips, and stationary sources. It showed that the recommendation does not affect air quality because the positive effects from retaining 92% of the existing public street trees and from providing safer non-vehicle travel options are offset by the potential for more emissions from increased vehicle travel time.

Environment

The recommendation does not require widening the roadway, and so makes no changes to the soil or to Twomile Canyon Creek, which is on the northeast corner of Broadway and Iris Avenue. Therefore, the recommendation does not require clearing, create an increase in hardscape (non-living landscape materials), or make changes to site ground features, like storm drainage or vegetation.

Nearby east-west streets all have indirect routes and challenging crossings. While nearby streets can offer lower-stress bike connections for some trips, they are not as direct and so do not serve all trips.

The city’s bike network serves diverse riders and trip purposes, and provides essential connections for recreation, exercise and transportation needs such as work, medical visits or school commutes. Although some of these trips may only use portions of Iris Avenue, all trips are better served by a safe and comfortable bicycle facility along the entire corridor.

While parallel routes are available for choice, prioritizing Iris Avenue for improvements offers the largest safety and connectivity benefits for our community. Unlike Iris Avenue, parallel streets suffer from disjointed intersections, making navigation tricky for people walking and biking. Just as the transportation network offers many options for vehicles, providing an all ages and abilities bicycle facility on Iris Avenue provides a direct option for people traveling by bike.

Iris Avenue from 19th Street to 28th Street is on the 2023-2027 Vision Zero Action Plan High Risk Network. The main crash types on Iris Avenue are rear-end and turn-related.

There have been a total of 345 crashes from 2016 through 2023, six resulting in serious injury.

• 143 of those were rear end crashes. 58 of those were approach turn crashes, turning across oncoming traffic.
• 22 of these crashes were pedestrian or bicycle crashes. In all cases involving people walking or biking, the person driving was at fault for not yielding at intersections or driveways.
• 45% of these pedestrian and bicycle crashes happened near the 26th Street and Folsom Street intersection.

The evaluation showed that the recommendation would reduce both vehicle crashes and vehicle-bike crashes. The recommendation’s roadway reconfiguration creates space for the highest quality safety improvements such as protected intersections, including at Folsom/26th Street.

• Lane repurposing from four lanes to three lanes can reduce vehicle crashes by 25% to 50%.
• Implementing a protected bike lane can reduce vehicle-bike crashes by 35%.
• By providing space for protected intersections, the recommended conceptual alternative also reduces common crash types and the severity of crashes when they do occur at intersections
• It will reduce the Vision Zero Action Plan common crash types that occur on the High Risk Network (right turn crashes and pedestrians/bicyclists crossing the street). It will also reduce the severity of crashes when they do occur by moderating vehicle speeds.

The recommendation reduces common crash types and the severity of crashes when they do occur at intersections by providing space for protected intersection elements.

Protected intersection corner islands reduce the risk of crashes by physically separating people walking, biking, and rolling from vehicles at intersections, shortening crossing distances and improving visibility for everyone. Data from national transportation guidance found increases in drivers yielding to people walking and biking following protected intersection installation.

Signals changes will separate vehicle, bike and pedestrian travel at Iris Avenue.

In detail: What is a protected intersection?

Learn what a protected intersection is and how to use it in this short video. This video was created for Boulder’s first protected intersection at 30th Street and Colorado Avenue, the city's first fully protected intersection.

People biking on two-way protected bike lanes travel in both directions on one side of the street.

The recommendation includes a two-way bike lane on the north side of Iris Avenue due to fewer conflict points, disaster emergency response benefits, and more sun exposure in the winter months than the south side, which helps melt snow. Between Broadway and 28th Street, the north side has 13 conflict points, while the south side has 34 total conflict points.

Two-way protected bike lanes:

• Include clear signage and markings as well as raised crossings where conditions allow.
• Lead to people biking experiencing fewer conflict points along the corridor than in one-way bike lanes.
• Are wide enough for easier maintenance. One-way protected bike lanes are narrower which requires specialized equipment for snow plowing as well as street sweeping.
• Are wide enough to allow for easier passing and side-by-side bike riding.
• Include adjustments to turn signal phasing to separate biking and vehicle turning movements to avoid conflicts when driving across the protected bike lane.
• Require intentional design at driveways and unsignalized intersections because people driving must expect people biking coming from both directions.
• Can be used as an emergency vehicle lane during a disaster emergency response.

We used community feedback, data analysis, technical expertise and best practices to develop conceptual design options presented to the community for input in 2024.

In Detail: How did you develop alternatives?

We consulted best practices, design standards and guidelines to identify all potential solutions to the issues identified by the data and community engagement to develop 13 possible design options for Iris Avenue corridor.

These 13 possible design options included a range of solutions that explored different bike and pedestrian facility types including off-street bike lanes and multi-use paths, as well as a range of lane configurations from two to five vehicle lanes. The designs were chosen because they supported plans, policies, and project and city goals and addressed the issues identified through community engagement, data analysis and preliminary traffic operations analysis.

Nine of the possible design options did not advance because of:

• Infeasible traffic operations. Preliminary traffic analysis found impacts to vehicle travel that could not be mitigated, like vehicles waiting through several traffic cycles or back ups blocking multiple intersections.
• Floodplain impacts. Floodplain analysis determined a design caused a rise in the Twomile Canyon Creek floodplain. A rise in a floodplain is not permitted for any project in the city.
• Cost impacts. Preliminary cost estimates of a design were beyond costs of comparable options with comparable benefits.
• Right-of-way impacts. Analysis determined designs required large easements or had impacts to existing structures.

Considerations

We used several key considerations to develop the final four conceptual alternatives, including:

• Consultations with city partners to consider disaster response, existing public street trees, utility relocation and stormwater drainage.
• Traffic Safety: Potential to reduce speeds and severe crashes on the corridor. This considered:
  • Vehicle speed moderation
  • Crash reduction
• Transportation Operations: Potential to impact vehicle travel time, vehicle turning movements and emergency response. This considered
  • Corridor vehicle travel time
  • Vehicle turning movements
  • Vehicular Level of Service (LOS)
  • Day-to-day emergency response
  • Disaster emergency response
• Safe and Comfortable Connections: Potential to enhance residential, neighborhood, and business access, low-stress walk and bike connections and transit experience.
  • Walking comfort
  • Biking comfort
  • Opportunity for protected intersection elements
  • Crossing safety and comfort
• Sustaining Tree Canopy: Potential to preserve existing street trees and maintain the current tree canopy.
• Implementation Feasibility: The amount of time and cost needed to design and implement the project.
  • Time to design and implement
  • Maintenance
  • Right-of-way property acquisition
  • Utility relocation and stormwater drainage
  • Implementation cost

Learn more about the alternatives development process on the Virtual Open House.

The recommended conceptual alternative design, Alternative B, provides the most safety benefits with lower costs and time to implement. While each alternative has trade-offs and competing priorities, Alternative B best balances community priorities, advances city policies and implements nationally recommended safety improvements.

In Detail: How was this recommendation selected?

City staff evaluated the four possible conceptual design alternatives using the city’s Community and Environmental Assessment Process (CEAP). The CEAP is a formal review process. It assesses the potential impacts of capital improvement projects to help select a recommended alternative. The evaluation considered potential social and environmental impacts, project-specific criteria and community feedback, which we’ve been collecting since last summer.

The city uses the CEAP process to identify a recommended alternative by evaluating each conceptual alternative against the criteria of the three cornerstone components of this process: the CEAP Checklist, Project-Specific Evaluation Criteria and Community Input.

The CEAP evaluated the four conceptual alternatives for the configuration of the roadway, advanced the overall design process, and developed a recommended alternative to share with the Transportation Advisory Board and City Council, which they approved in fall 2024.

Learn more about the selection process on the Virtual Open House.

During the alternatives development process, we heard that safety is the primary concern, followed by high vehicle speeds and increased traffic congestion. Community feedback supports improving safety and comfort for biking, walking and crossing Iris Avenue. There was also a request for the city to recognize Iris Avenue’s role as a key east-west driving route and consider removing the bike facility from Iris Avenue.

The recommendation responds to the highest community priorities for crash reduction, moderating vehicle speeds, providing bike and pedestrian comfort and preserving trees with minimal added travel time. It also addresses the community priorities of emergency response, reduced time and cost to implement, and limiting utility impacts.

The CEAP and recommendation were shared with the Transportation Advisory Board for their review and recommendation on Sept. 9, 2024. The recommendation was brought to City Council, who approved at their Sept. 19, 2024 meeting. Final design will start in 2025 and implementation will follow as funding is secured.

In addition to speeding on Iris Avenue, speeding on side streets is a concern and affects the safety and quality of life for people who travel on the street or live nearby. We’ve heard from the community that some people driving currently avoid Iris Avenue to speed on these side streets. The neighborhood is concerned that this speeding will increase because of the Iris Avenue Project.

Since hearing these concerns, we have begun work on a concurrent project to help prevent speeding on side streets.

We will identify specific locations for speed mitigation installations along these side streets, prioritizing street segments with the largest speeding problem. These changes will support considerable public investments over the last two decades in neighborhood speed mitigation on streets with direct connections to Iris Avenue.

This work will begin when construction for the Iris Avenue project is in progress. We will monitor additional street segments for increases in traffic and speeds.

• City Council Agendas and Materials
• Transportation Advisory Board Records

2024 Community Engagement

While 2024 community engagement is ongoing, you can view past materials and summaries on the June 27 City Council Project Update. For more up-to-date information, view the open houses.

2023 Community Engagement Report

Thank you to everyone who walked, talked, or otherwise participated in one of the 24 engagement activities the Iris Avenue Transportation Improvements project team hosted in 2023! Over 1,300 people shared valuable time and knowledge with us. View all the details in the full 2023 engagement report.

These projects are happening at or near Iris Avenue, but are not part of the Iris Avenue Transportation Improvements Project.

Crosswalk Improvements

In late 2024, we plan to construct pedestrian and bicycle enhancements to Iris Avenue at the 15th Street crossing. While these crossing improvements support our CAN goals, they are not part of the Iris Avenue Transportation Improvements Project. We received funding from the Denver Regional Council of Governments (DRCOG) Community Mobility Planning and Implementation 2019 grant program to improve three crosswalk locations, including at this crossing.

Learn more about the city’s Pedestrian Crossings.

Sanitary Sewer Rehabilitation

There is ongoing sewer work, including liner installation, on Iris Avenue from Broadway to 28th Street, and in the neighborhoods to the south. There may be traffic and parking impacts. Learn more about the Sanitary Sewer Rehabilitation Program.

This section provides text alternatives to the webpage graphics. The city is in the process of making all of its websites and applications more accessible. If you would like assistance, contact the city's ADA Coordinator using the Accessibility Complaint or Request Form or by calling 720-576-2506. Please know that the city is happy to assist you and do not hesitate to reach out.

Project context map long description

This is a text alternative to the project context map graphic. The core study area extends east and west on Iris Avenue from Broadway to US-36/28th Street. The secondary study area extends east to west from the same limits, and north to south from roughly Norwood Avenue to Balsam Avenue/Edgewood Drive. On the core study area, there are bookend improvements with no changes to existing vehicle lane configuration: west of the project limits, there are Broadway Bookend Improvements from Broadway extending east to Hawthorn Ave; east of the project limits, there are 28th Street Bookend Improvements from just east of Folsom Street extending east to 28th Street. Between 13th Street and Folsom Street/26th Street, which is the area excluding the bookend improvements, the core study area includes end-to-end improvements including protected bike lanes as well as sidewalk and bus stop upgrades. This area also has four conceptual design alternatives developed.

Timeline long description

This is a text alternative to the project timeline. Community engagement extends from the beginning to the end of the project. From summer to winter 2023 is Corridor Analysis: understanding what is working and what needs improvements. During winter 2024 is Initial Screening: What improvements are technically feasible? Begin development of improvement options to address what we heard. From winter to spring 2024 is Alternatives Development: What improvements or alternatives are best to address the project goals? Project team began to develop conceptual alternatives to address what we heard. In spring 2024 is Share Conceptual Alternatives: Share conceptual design alternatives with community for feedback. In Summer 2024 is Recommended Alternative: What is the recommended alternative? Project team develops recommendations as part of the Community and Environmental Assessment Process (CEAP). This is the current phase. After this phase is the future, with Final Design and Construction: What is implemented and when, will depend on the final design and the funding available.

2023 Community Engagement Report Alternative

This is a text alternative to the PDF report.

What did we hear?

Summary of themes from 2023 community engagement:

• East-west travel is important, and people driving appreciate Iris Avenue as a convenient and reliable route across the city.

• People walking, rolling, biking and taking transit also want Iris Avenue to provide convenient and safe routes.

• Sidewalks could be improved to provide comfort, safety, and attractive walking conditions. Sidewalks are currently: not wide enough, winding, sloping, bumpy, and often blocked by overgrown vegetation.

• Crossing Iris Avenue safely and conveniently is a priority for people of all ages and abilities traveling to school, work, for errands, and for recreation – but today some see it as a barrier to getting where they want to go.

• Vehicles travel at high speeds, creating unsafe conditions and excessive street noise.

• Safer neighborhood and business access is essential.

• Drivers feel unsafe turning onto and off Iris Avenue and feel they’re more likely to crash with oncoming traffic when doing so.

• Delivery, transit, waste management and other vehicles stop in-lane, blocking the bike and right-side travel lanes.

• Residents are concerned changes will impact emergency evacuation and response.

• Neighbors want to maintain the character of their neighborhoods, which they see as providing safer, more comfortable alternatives for walking, rolling, and biking than arterial streets like Iris Avenue are concerned that changes to Iris Avenue could create traffic diversion onto nearby streets.

• Community members want attractive facilities and opportunities for placemaking.

• Beter wayfinding and help navigating to local and regional destinations are desired.

• Roadway pavement conditions could be improved.

• Transit service is infrequent, and many transit stops are not accessible and lack shelters, benches, and trash cans.

Who did we hear from?

We heard from:

• Residents, employers and employees at pop-ups, through online questionnaires, and at an open house.
• Children, youth and families shared their experiences traveling along and across Iris Avenue when we met them at their schools and when they walked Iris Avenue with our partners at Growing Up Boulder.
• Advocacy organizations like Boulder Walks, Community Cycles, and the Center for People with Disabilities gave voice to the experience of walking, biking, rolling and strolling the corridor today.

What events were there?

Past community engagement events in 2023 included:

• Dec. 16: Winter Walks in the Park at Melody Park from 11 a.m.-noon
• Dec. 9: Winter Walks in the Park at Columbine Park from 11 a.m.-noon
• Dec. 2: Winter Walks in the Park at Parkside Park from 11 a.m.-noon
• Oct. 24-Nov. 8: Virtual Open House
• Oct. 24: Open House, 5:30-7:30 p.m
• Sept. 27: Guided Biking Tour
• Sept. 19: Guided Walking Tour
• Sept. 16: Fall Transportation Safety Fair
• Sept. 14: Boulder Junction Funktion
• Sept. 13: Growing Gardens Pop-up
• Sept. 10: What’s Up Boulder
• Sept. 6: Elmer’s Two Mile Pop-up
• Aug. 31: CU Bike Fest
• Aug. 30: Foothill Elementary Pop-up
• Aug. 30: Columbine Elementary Pop-up
• Aug. 9: Red Oak Park Bike Giveaway
• Aug. 6: Accessible Roll and Stroll
• Aug. 1: National Night Out

Community engagement also included a questionnaire and interactive map during summer 2023.

Stay tuned for Iris Avenue project updates on the project email, the Transportation and Mobility Department newsletter or the project webpage.