POSTED Tuesday, March 18, 2013 --- 11:00 p.m.
Reporter: Phil Levin
If you are still getting used to roundabouts, get ready for the state's first diverging diamond interchanges, which could be constructed in Dane County.
The Department of Transportation is planning reconstruction of Stoughton Rd. between McFarland and DeForest that could cost $200-850 million beginning in 2020. Included in proposed plans are new interchanges at the Beltline and Highway 30.
The diverging diamond pattern could save hundreds of millions of dollars in construction by reusing existing bridges. The traffic pattern involves brief stops for drivers continuing through the intersection, but no stopping for some exits and entrances. The design eliminates perpendicular traffic which can cut down on collisions.
Currently, there is about one crash per day on the 13-mile stretch of Stoughton Rd. About a third of those incidents involve injuries, including at least five deaths since 2007.
DOT Planning Supervisor Mike Hoelker says if nothing is done by 2040, every intersection along the stretch will be "failing," meaning the average wait will exceed about a minute.
To combat the congestion, plans call for lowering the road below cross streets like Pflaum Rd and E. Washington Ave.
A revised proposal is expected in September. Phased construction could begin in 2020, but the timeline depends on other projects throughout the state.