New, wider Fourth Street bridge complete in Flagstaff

Bridge offers improved traffic flow for vehicles, bicyclists, pedestrians

Fourth Street bridgePHOENIX – The new Fourth Street bridge passing over Interstate 40 in Flagstaff is now complete, providing improved safety and traffic flow in the area.

The Arizona Department of Transportation used an innovative accelerated bridge construction method known as the bridge slide to construct the new bridge and complete the project in just over six months.  The slide method allowed ADOT to construct the bridges to one side, then slide them into place over one long closure which greatly reduced the impact to the traveling public.

The new bridge has two lanes in each direction, a center turn lane and a protected path for bicycles and pedestrians on one side and a sidewalk on the other. The protected path connects the Flagstaff Urban Trail System across the interstate.

The city of Flagstaff paid for half of the cost of the new Fourth Street bridge in addition to covering the cost of aesthetic enhancements.

This project also includes a resurfaced bridge deck and repairs to the pavement approaches to the Butler Avenue bridges over I-40. The total cost of the project for both bridges is $13.9 million.

For its use of accelerated bridge construction techniques on this project, the Federal Highway Administration granted the Arizona Department of Transportation an extra 5 percent of the construction cost on top of the normal federal allocation under its Increased Federal Share program. The federal allocation reduces the state's costs, and this extra money allows ADOT to put that portion of state Highway User Revenue Fund proceeds toward other priorities.

ADOT has been using different innovative methods to accelerate bridge construction for different bridges along I-40. This is the second time in the past year ADOT has used the bridge slide method. The first time was installing new Bellemont bridges at I-40 and Hughes Avenue, formerly Transwestern Road, west of Flagstaff. 

Also last year, the agency used a process known as a geosynthetic reinforced soil-integrated bridge system to rebuild the bridges on I-40 at Meteor City Road, creating abutments by putting in alternating layers of granular fill reinforced with synthetic material. That process also cut construction time by months.