According to the U.S. Office of Research and Technology, there were just under 92 million total registered highway vehicles in the United States in 1965. Some 50 years later, that number tripled to over 260 million vehicles, illustrating the exponential growth in the amount of overall traffic on today's roads and highways.

As with most interstate highway systems throughout the country, existing roads and bridges are in need of updates and improvements. A prime example of ongoing efforts to bring roads and bridges up to current standards is the I-96/U.S. 23 interchange in Detroit's far northwest suburbs. Constructed in 1962, this interchange allows for east-west commuter access along I-96 to Detroit and Lansing from Ann Arbor and Flint, and for local access to the greater Brighton area. Initially constructed for the slower speeds and lighter traffic that existed at that time, a goal of this project has been to include safety and operational improvements by separating higher speed freeway traffic from slower moving ramp traffic.

The Michigan Department of Transportation's (MDOT) improvements to the I-96/U.S. 23 interchange in Brighton Township, Livingston County include:

• Constructing new through-lanes on I-96 between the current eastbound and westbound lanes, which included construction of three new bridges over northbound and southbound U.S. 23, and over Old U.S. 23.
• Converting existing lanes of I-96 to collector-distributor (CD) lanes for easier and safer lane changes for ramp traffic, which included the reconstruction of six existing bridges.

The general contractors for the project are Toebe Construction LLC, based out of Wixom, Michigan, and Kamminga & Roodvoets, Inc. based out of Grand Rapids, Michigan. The project also included 28 subcontractors, who were used in various support roles during the duration of the project.

Improving a Hazardous Area

One of the busiest interchanges in Michigan outside the Metro Detroit area, the I-96/U.S. 23 junction includes two left hand exit and entrance ramps, compressed merge areas and a long section of high speed, curving expressway with rolling grades. Also, the short distance between ramp entrance and exits slows down traffic and creates a safety hazard. Faced with task of replacing bridges that were at the end of their service life and concerned with the impact this would have on commuters during construction, MDOT supported a solution that addressed both the bridge condition and improved the safety and operation of the interchange as a whole.

Of particular concern to MDOT were the two existing freeway-to-freeway left hand exit and entrance ramps, which merged slower moving ramp traffic with faster moving freeway traffic. Mark Sweeney, Manager of the Brighton Transportation Center for the Michigan Department of Transportation, said, "We didn't have the opportunity to address this situation until the area bridges were at the end of their service life and needed repair and replacement.  At that point, our designers searched for a resolution, which was supported by the local Federal Highway Administration office."

MDOT's solution created new express lanes between the two existing lanes of eastbound and westbound I-96 to carry the through traffic, thereby turning the existing lanes into collector- distributor lanes for the slower moving ramp traffic.  "So, though we still have traffic merging in from the left, it's doing so at a slower speed and with less traffic," commented Sweeney. "This has introduced a number of associated challenges."

Performing the Environmental Study

As with all federal aid projects, an environmental clearance process was followed, with MDOT conducting the required analysis. "We were required to do this study," noted Sweeney. The study evaluated the potential noise impacts and abatement of the proposed improvements at the I-96/U.S. 23 and Spencer Road interchange in conformance with corresponding Federal regulations and guidance and the National Environmental Policy Act (NEPA). Noise abatement solutions usually include modeled noise barriers, which are typically seen in urban and highly populated areas. Based on the completed analysis, no noise abatement for the I-96/U.S. 23 interchange project was recommended.

The I-96/U.S. 23 improvement project began in spring 2015 and is expected to be complete this fall, with investment of local, state and federal funds at $70 million. This included a winter shut down that began in December 2015, with work resuming again in April.