New, wider Fourth Street bridge completed in Flagstaff, Arizona

Oct. 21, 2020

Accelerated construction method used to construct new bridge and complete the project in just over six months

The new Fourth Street bridge passing over I-40 in Flagstaff, Arizona is now complete, providing improved safety and traffic flow in the area.

The Arizona DOT (ADOT) 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 ADOT an extra 5% 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.