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Diagonal Highway Transportation Improvements

Project Update

The project construction is complete!

Public art has been installed in winter 2018.

For mor information, contact:

Noreen Walsh● Transportation Division ● 303-441-4301● [email protected]

Project Background

The Diagonal Project is a City of Boulder, Transportation Capital Improvements project. Work began in August 2015, to transform a section of the Diagonal Highway, between 28th Street and Independence Road, into a multi-modal corridor and gateway to and from Boulder, with a new roadway surface, multi-use path, off-street protected bicycle lanes, and upgraded transit stops, while maintaining the existing vehicular lanes. The improvements contribute to a safer and more efficient travel experience for drivers, transit users, pedestrians, and cyclists.  Additionally, 400 trees and over 6,000 new shrubs and plants will be planted and public art will be installed creating a gateway to/from the city.     


The Diagonal Highway Transportation Improvements Project pdf started in August 2015 and was completed at the end of 2016.  There will be some final finish work and a public art installation in the summer of 2017.

Project Improvements

View Diagonal Highway Illustrative Plan of Project Improvements pdf

The Diagonal Project will provide the following improvements:

  • Reconstruction of the existing deteriorated street pavement between 28th and 47th streets.  
  • Construction of a new multi-use path, off-street bicycle lanes (also known as cycle track), medians, transit stops bus pads, and other amenities.
  • Re-striping of the roadway to add buffered, on-street bike lanes between Foothills Parkway and Independence Road.
  • Installation of public art, trees and landscaping to create a "Gateway" to and from Boulder.
  • Installation of new curbs, gutters, storm drains, water quality systems, and irrigation systems.

Innovations and Sustainable Features

The Diagonal Project will reconstruct the highway to improve the existing lanes while adding off-street bicycle lanes for cyclists and a multi-use path for pedestrians.  The separation of drivers, pedestrians, and cyclists will lead to safer travel.

The Diagonal Project will feature an off-street bicycle lane, also known as a cycle track.  A cycle track is primarily used for bicycles.  It combines design features of a separated path with the on-street infrastructure of a conventional bike lane. The Diagonal Project cycle track will be physically separated from vehicular traffic and distinct from the new multi-use path.

The Diagonal Project will also install rain gardens.  Rain gardens are low-lying areas landscaped with plants, mulch, and soil on the surface, and sand beds and drains underneath.   These rain gardens will collect, store, and filter rain water and storm water runoff, naturally removing pollutants. 

The project will re-use 100 percent of the old asphalt roadway as a base layer for the new concrete roadway.  This sustainability feature saves money and reduces greenhouse gas emissions by eliminating the need to transport the removed asphalt out and new base layer material in.  

The project will increase the city’s tree canopy through planting of over 400 new trees.  The city’s tree canopy has decreased in recent years due to the emerald ash borer’s impact on the green ash tree.

Funding and Budget

This project is part of the Regional Transportation Improvements Program (TIP) and is funded by the City of Boulder, the Federal Highway Administration (FHWA) and the Colorado Department of Transportation (CDOT). The city also applied for and was awarded additional funding from the Colorado Department of Transportation's (CDOT's) Responsible Acceleration of Maintenance and Partnerships (RAMP) program. This additional funding allowed the project to expand from its original eastern projects limits of 30 th Street to Independence Road.

The project budget of $11 million is composed of City of Boulder transportation funds, federal transportation funds and Colorado Department of Transportation funds.  

Previous Videos About This Project

Project Update From Nov. 2, 2016 edition of Inside Boulder News

Project Update from July 29, 2016 edition of Inside Boulder News 

Public Involvement

Planning and design of this project began in 2013 and a public meeting was held on May 20, 2013.

View existing traffic data pdf

Diagonal Highway Existing Conditions

Diagonal Highway (28th to 30th Streets) Reconstruction Project - BeforeDiagonal Highway (28th to 30th Streets) Reconstruction Project - BeforeDiagonal Highway (28th to 30th Streets) Reconstruction Project - BeforeDiagonal Highway (28th to 30th Streets) Reconstruction Project - BeforeDiagonal Highway (28th to 30th Streets) Reconstruction Project - BeforeDiagonal Highway (28th to 30th Streets) Reconstruction Project - Beforewestbound lanes_completed_after_switch3westbound lanes_completed3westbound lanes_completed_after_switchwestbound_travel_lane_work_Photo Nov 24, 1 27 44 PM

See full photo set in the Photo Gallery