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Problem

High traffic volumes and speeds were creating an unsafe and unpleasant walking and bicycling environment along 55th Street in Boulder, Colorado.

Background

Residents near 55th Street were concerned about speeding vehicles and high traffic volume in the corridor where the posted speed limit was 56 km/h (35 mi/h). Residents had difficulty entering 55th Street from numerous side streets, and they had expressed concerns about the difficulty of crossing and the unpleasantness of walking along 55th Street. They believed that prior improvements on nearby Cherryvale Road, made by Boulder County, had diverted excessive traffic onto 55th Street and exacerbated this problem.

Solution

A Capital Improvement Project was implemented to provide improved bicycle and pedestrian facilities in the corridor, and to provide some traffic calming for vehicles. The following improvements were made:

• A continuous sidewalk was constructed on the eastside of 55th Street.
• Bicycle lanes were provided on both sides of 55th Street.
• A bicycle/pedestrian underpass was constructed along the Centennial Trail alignment.
• Two raised crossings and one raised intersection were constructed, with pedestrian refuge islands at both of the raised crossing locations.

The project intended to improve transportation operations for all modes of travel by providing a number of transportation upgrades, including bicycle lanes, pedestrian facilities, speed mitigation devices and left turn access lanes on 55th Street. Intersection improvements at the Arapahoe Road and Baseline Road intersections were also a part of the project. To accomplish these goals, approximately $1.7 million was spent to construct the improvements.

Results

Staff conducted a before and after study by collecting transportation data before and after the project and comparing the results of this data collection with the goals of the project. According to the study, both travel speeds and traffic volumes decreased after the completion of the project. Table 1 shows that approximately 3,000 vehicles appear to have been diverted from 55th Street.

A review of the peak hour traffic volumes at the intersection of Arapahoe and 55th Street showed reduced traffic volumes traveling north-south through the intersection following the project (see Table 2).

A corresponding increase in traffic turning to and from 55th Street north of Arapahoe Road suggested that traffic was diverting east and west along Arapahoe Road instead of traveling north-south on 55th Street between Arapahoe Road and Baseline Road.

Travel speeds in the corridor were significantly reduced, and the 85th percentile speed in the corridor is closer to the speed limit than it was prior to project construction. There was substantial traffic diversion as a result of the project, but it does not appear that this diversion has caused any other issues in the area. The diverted traffic appears to have been dispersed to several different roadways or eliminated.

With the addition of several improved bicycle facilities, the amount of bicycle activity in the corridor is substantially higher than it was prior to construction of the project. However, a safety issue developed at the intersection of 55th Street and Arapahoe Road, where bicycles were being hit by turning traffic.

Pedestrian improvements appear to have met with mixed success. The new underpass is well utilized, but there does not appear to be any other increase in pedestrian activity in the corridor. Overall, the decrease in traffic speeds and volumes has increased pedestrian safety along the street.

Contact

Bill Cowern
Transportation Operations Engineer
City of Boulder
PO Box 791
Boulder CO 80306
Phone: (303) 441-3266
Fax: (303) 441-4271
E-mail: CowernB@ci.boulder.co.us

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