I-15 Expansion Alleviates Traffic Congestion

Stanley Consultants developed and evaluated 22 alternatives to eliminate the congestion on Utah's Interstate 15.

Each afternoon, a bottleneck formed on Utah's Interstate 15 where the number of lanes dropped from five to three in the southbound direction.  With average daily traffic of 125,000 vehicles, the Utah Department of Transportation (UDOT) estimated the congestion resulted in a user cost of $35,000 per day. Using a weighted evaluation matrix developed for project criteria, a 9-8-10 lane solution (9 lanes south of Bangerter Highway, 8 lanes under the Bangerter Highway overpass and 10 lanes north of Bangerter Highway) was developed to handle projected traffic volumes for the next 15 to 20 years.  Final design of the fast-track $37 million project occurred in just six months. 

For safety reasons, UDOT required that all new lane locations correspond to existing lane locations so the concrete pavement joints followed the lane lines.  For just the second time in Utah, asphaltic bonded concrete wearing course was used to accomplish this goal.  

Many innovative elements were incorporated in the project.  An "in-house" custom developed software program was used to re-establish the existing centerline alignment to within six inches of the original alignment. 

A unique review process was implemented to reduce the review time and begin incorporating review comments prior to completion of the review.  A + B bidding (construction costs + schedule costs) was used to provide incentives for the contractors to finish the major construction items in the 2004 construction season.  The project was designed to accommodate future improvements such as managed lanes or reversible lanes without reconstruction of improvements made by this project.