GREENWOOD, Ind. – State highway officials hope to make Indiana the latest state to try a new highway ramp design that aims to lower construction costs and make travel easier.
The Indianapolis Star reports (http://indy.st/13VZ9Cm) that planners with the Indiana Department of Transportation are discussing building a diverging diamond interchange along Interstate 65 in Greenwood, south of Indianapolis. A similar project is planned along Interstate 69 in Fort Wayne.
The Journal Gazette’s Road Sage column reported about the diamond-interchange plan for the Dupont Road interchange in 2012. To see how the design works, click here.
Diverging diamond interchanges crisscross east- and west-bound lanes to allow cars to enter highways without turning left in front of oncoming traffic.
“The downside is it’s something new,” INDOT engineer Susan Doell told the Star. “People are going to have to get used to it.”
The design is safer than a more traditional cloverleaf-style interchange because there is a “lack of weaving and (a) big differential of speeds between the loop ramps and the through traffic,” Gilbert Chlewicki, a Maryland engineer, told the Star. There are also signals that control traffic at both points where the lanes cross.
The interchanges would be the first of their kind in Indiana, but seven other states so far have built them. States that have adopted the diverging diamond design have saved millions of dollars. The design is more compact than traditional cloverleaf interchanges and tends to be cheaper.
Diverging diamond interchanges have also been proven to reduce crashes in some areas. A study shows that in St. Louis, the diverging diamond interchange showed a 38 percent drop in crashes with no wrong-way crashes. Officials in Springfield, Mo., say the design reduced crashes by 50 percent at the city’s two diverted diamond interchanges.
A diverging diamond design in Greenwood could save taxpayers $3 million when compared to more traditional designs. Savings in Fort Wayne would range from an estimated $3 million to $6 million.
The state Department of Transportation will conduct public meetings to get feedback before deciding whether to adopt the new designs. If the interchange proposals are approved, the new interchanges could open by 2014.