Expansions, new interchange designs still in the running for I-43 renovation

April 2, 2013

An expansion of Interstate 43 in the Glendale area is nearing certainty as the state Department of Transportation sifts through community input in the planning stages of its upcoming highway renovation project from Silver Spring Drive in Glendale to Highway 60 in Grafton, tentatively slated for 2019.

DOT officials briefed area government officials and community representatives last week on the project's progress, indicating in most cases that spot improvements or "do nothing" approaches which wouldn't increase highway capacity are off the table. Plans for the project, DOT officials said, are meant to increase safety, bring the highway up to modern design standards, and increase the capacity of I-43 to accommodate projected 2040 traffic counts.

Community input has been generally supportive of expanding the highway from four to six lanes in the Glendale area, said DOT Project Manager Steve Hoff, as well as mostly supportive of building a new interchange at Highland Road in Mequon. To handle the projected traffic increases the DOT may use high-capacity interchange designs which haven't yet been used in Wisconsin.

"The public education component would be pretty big here," Hoff said.

Mainline, Highland Road expansions likely

With the options for spot fixes and an updated four-lane design along the "mainline" section of I-43 between Bender Road and Green Tree Road off the table, the DOT is moving forward with expanded six-lane options that could shift that section of the highway east, west, or keep it centered where it is now.

DOT is also still considering options that could slightly depress the mainline into the earth or raise it up to an apex of 60 feet off the ground to go over the railroad that crosses over the highway. Though area officials and residents have been critical of the raised option, Hoff said it's still in the running because it would cause the least amount of property acquisitions.

"That's the one with the real minimal impact," Hoff said.

While some had suggested the mainline be buried and covered to create a tunnel, Hoff commented that drainage issues and a high water table drowned the idea.

"We can't really get it down far enough to bury it," he said.

According to DOT officials, Mequon residents at previous public information meetings have favored a Highland Road interchange at about 3-to-1.

Mequon City Administrator Lee Szymborski said the city will include questions about the possibility of a Highland Road interchange in an upcoming survey.

According to the survey, the city's share - based on a 50/50 split between Mequon and the DOT - is estimated at $7.5 million, which would cost the average Mequon homeowner between $30-$50 annually over a 20 year period.

Szymborski said that the city may try to partner with area communities to share the cost of the interchange.

New designs

Along with a standard diamond-shaped design, the DOT is considering using a "single point" design at the Good Hope interchange. The single point design converges through-traffic, as well as traffic entering and exiting the freeway, into a single intersection on the overpass.

Below: Videos demonstrating the function of the single point (top) and diverging diamond interchange (bottom) designs.

The single point design is simpler and can handle more traffic, Hoff said, though the overpass would need to be widened to accommodate the large intersection.

Preliminary designs also include a new off ramp for drivers meaning to go north on Port Washington Road. The new ramp, meant to prevent drivers from having to quickly cross lanes to reach the left-turn lanes at Good Hope and Port Washington, would have drivers exit onto the intersection of Port Washington Road and Sugar Lane.

The DOT plans to replace the clover leaf interchange at Brown Deer Road, Hoff said, and is looking at another new-to-Wisconsin design to accommodate traffic.

The "diverging diamond" design crisscrosses over the highway, causing drivers to temporarily drive on the left side of the overpass between traffic signals. Like the single point design, a diverging diamond increases capacity and overall safety, Hoff said, but may seem unintuitive to a someone encountering it for the first time.

Indeed, Hoff said, selling the public on the merits of the unfamiliar single point and diverging diamond designs may be a focus of the next public information meeting, scheduled for August.

"They could function well," he said, "but they're new, and people are a little leery of that."

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