The Interstate 96 interchange at Wixom Road in Wixom, MI, is being reconstructed into a Single Point Urban Interchange (SPUI). In a SPUI, a single traffic signal at the center of the interchange controls all left-turns. Drivers make opposing left-turns at the same time under the protection of this traffic signal. SPUIs can:
- Be constructed where there would not be room for a standard interchange, which is ideal for urban areas
- Allow more vehicles to make a turn and clear the interchange in one traffic signal cycle
- Be coordinated with cross-street signal systems
- Allow long, gradual turns so larger vehicles have more room to navigate
A P-1 concrete mix is being used on the interchange. Dan's Excavating, Inc., of Shelby Township, MI, is the prime contractor, and John Carlo Inc., of Clinton Township, MI, is the paving subcontractor.
"There is a lot of variable-width paving in a tight area on this project. It required a few paver changes and a lot of hand placements in order to meet the variable-width requirements," Jason Fowler, quality control manager for John Carlo Inc., said.
"The lanes are standard width going up the ramp, but as you go up the ramp and everything starts branching off to Wixom Road, certain lanes get wider and narrower. So, figuring out how many pavers to send out and at what width and how much handwork to do was somewhat of a challenge."
Dennis Cooper, delivery engineer for the Michigan Department of Transportation (MDOT), said that the schedule for the project is tight and there has been a great deal of mechanically stabilized earth (MSE) wall on the project, which has also been a challenge.
"We are using straw logs on the steeper slopes in order to prevent erosion. They are trenched in horizontally along the slope parallel to the roadway. They slow down the water that comes off of the road and goes down the slope. Normally, it will cause erosion. The straw slows the water down at certain intervals so that it doesn't reach erosive velocities. It helps protect the slope until the grass can get established," Cooper said.
Materials on the project include 78,000 square yards of concrete pavement and shoulders; 310,000 cubic yards of embankment; 150,000 cubic yards of earth excavation; approximately 750,000 pounds of reinforcement steel; and 3,300 cubic yards of structural concrete for the bridge work. The surface area of the bridge deck covers 4,560 square yards.
"One of the bigger challenges is constructing this much in such a small space. The intention of the Single Point Urban Interchanges is to reduce the acreage that it takes to build an interchange," Brian Olesky, project manager for Dan's Excavating, Inc., said. The contractor has used precise scheduling in order to meet the challenge.
"You have to make sure that the right people and the right subcontractors are in the right place at the right time so you don't get congestion on the project," Olesky said.
Subcontractors on the project include: Metropolitan Power & Lighting, of Imlay City, MI (signals and lighting); P.K. Contracting, of Troy, MI (striping); and Ajax Paving Industries, of Troy (bituminous). Parsons Brinckerhoff and HNTB are the consulting engineers for the project. The $20-million project began in March and is expected to be completed in 2009.