21st Ave. and Main St. Intersection Improvements Project - City of Longmont
View of the intersection of 21st Ave. and Main St. in Longmont, Colorado taken from the northwest corner.

Project Overview

As Longmont continues to grow, the City must focus on transportation that serves everyone.

 

The City of Longmont’s 21st Ave & Main St Multimodal Improvements Project will study the intersection at Main St and 21st Ave in an effort to improve the intersection for all users. The study will identify upgrades to safety and connectivity at this intersection with an emphasis on improved pedestrian and bicycle access.

 

This project will benefit the community by providing a safer and more comfortable intersection at Main St and 21st Ave in the northern part of the city.

 

Project Update

The City of Longmont has chosen a protected intersection with raised medians as the intersection concept for 21st Ave. and Main St.

View of a pedestrian crosswalk with white stripes and green bike lanes, looking towards a corner with traffic signals in Davis, California. This is an example of a protected intersection in Davis, CA; Source: Google Maps

Example of protected intersection in Davis, CA; Source: Google Maps

 

Goals & Planned Improvements:

Based on thoughtful feedback from the community, transportation analysis and engineering best practices, the City chose to combine the protected intersection concept with raised medians. 

 

Overall, the community preferred the protected intersection. While this design concept alone would improve the pedestrian and bicycle safety, the addition of raised medians on Main St. will be more effective at reducing vehicle turning speeds. Together, these improvements will build a safer and more comfortable intersection for pedestrians and bicyclists.

A top-down illustration of a redesigned intersection with features to improve safety for people walking, biking, and using mobility devices. The design includes wide, marked crosswalks, protected bike lanes with green paint, and raised medians that provide safe waiting areas. Curb ramps are added at all corners for accessibility. Pedestrian islands and setback crossings give more space and time to cross safely. The layout separates people walking and biking from turning cars to reduce conflict and improve visibility. Trees and landscaping are included along sidewalks for added comfort.

Improvements and benefits of the intersection: 

    1. Bicycle crossings across both Main St. and 21st Ave.
    2. Bicyclists physically separated from vehicles at the intersection.
    3. Shorter crossing distances for pedestrians and bicyclists waiting to cross the intersection.
    4. Drivers can more easily see pedestrians and bicyclists waiting to cross the intersection.
    5. Bicyclists can make left turns without riding in vehicle lanes.
    6. Bicycle ramps at intersection corners smooth bicycle transitions.
    7. Median provides refuge for crossing pedestrians.
    8. Median reduces left-turn speeds for vehicles.
    9. Widened bridge over Oligarchy Ditch improves road alignment and signal operations.

 

Improvements to the intersection will also include:

  • Protected left-turn arrows  
  • Removal of channelized right-turn lanes
  • No right-turns on red
  • Reflective traffic signals for increased visibility
  • Pedestrian and bicyclist head starts on crosswalks
  • Longer crossing times for pedestrians and bicyclists
  • Narrower vehicle lanes to encourage slower driving speeds

 

Public Engagement  

Thank you to everyone who participated in the engagement process for the study phase of the 21st Ave. and Main St. Intersection Project – we heard from over 1,200 community members!  

Public Engagement Summaries:


This is what we heard: 

  • The 21st Ave. and Main St. intersection is not working well for drivers, pedestrians or bicyclists. 
  • 81% of survey respondents who walk/roll and 79% who bicycle/scoot feel “very unsafe” or “unsafe” when crossing the intersection. 
      • WHY? Crossing times are short, crosswalks are long and not protected, sidewalks are narrow and close to the street, cars speed and do not yield to pedestrians and bicycle facilities are disconnected. 
  • Drivers noted a need for protected left turn arrows on 21st Ave. They also expressed confusion about street layout with curvy lanes, uneven surfaces and a lack of one-way signage. 

 

 

Project Study Limits

Map of north Longmont with an orange box around the intersection of 21st Ave. and Main St.

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