Autoplay settings
Off On


Designing a Single-Point Urban Interchange for a New Bridge in Michigan

US-131 at M-179 Single-Point Urban Interchange
Photo courtesy of Michigan Department of Transportation (MDOT) Photography Unit
Tetra Tech designed a single-point urban interchange for a grade-separation bridge, successfully addressing site constraints, structural complications, and funding limitations.


Traffic at the US-131/M-179 interchange in Hopkins and Wayland Townships in Michigan increased with growing business at a nearby casino. The existing 33-foot-wide, 4-span bridge needed to be replaced to improve traffic flow at this interchange. The new bridge had to stay within the interchange’s right-of-way, and construction costs had to be managed to stay within funding limits.

The need for a wider bridge that is short enough to stay within the right-of-way called for a unique design to prevent cracking in the concrete bridge deck. Deck cracking is a common issue for bridges more than 100 feet wide. Normally, longitudinal expansion joints are used for wide bridges; however, these cannot be used when traffic crosses the joint at an angle.


Tetra Tech provided design engineering for both the roadway and bridge for a single-point urban interchange (SPUI). The SPUI was constructed at this location to increase capacity and enhance safety.

The new bridge is a 143-foot-long, 2-span prestressed concrete I-beam bridge. Our team incorporated multiple design details the delivered a safe structure that addressed site constraints within budget, including:

  • 195-foot width accommodates the turning movements required at the center of the interchange
  • Mechanically stabilized earth (MSE) retaining walls in front of integral abutments supported on a single row of piles minimize bridge length and costs
  • Design details for guided bearing restrainers allow for thermal movement in the transverse direction to prevent concrete deck cracking


  • Reduced construction and maintenance costs by incorporating flared ends of bridge deck for vehicle turning
  • Eliminated deck cracking concerns by creating guided bearing restrainer detail
  • Reduced deck area by decreasing span lengths using integral abutments behind MSE walls
  • Enhanced the visual appeal by incorporating custom aesthetic details

The Gun Lake Tribe of Pottawatomi Indians, local residents, Allegan County Road Commission, and Michigan Department of Transportation celebrated a ribbon-cutting ceremony for the bridge. This project promoted the economic prospects of the casino by making it easier and safer to get there from the freeway.

US-131 at M-179 Single-Point Urban Interchange
Photo courtesy of MDOT Photography Unit
Scroll to Top