Indiana drivers may someday find themselves driving on the wrong side of the road briefly near interstate on-ramps as part of a new traffic pattern called the diverging diamond that supporters say cuts down on traffic congestion, is safer and costs less to build than traditional cloverleaf or diamond designs.
The first diverging diamond in Indiana reportedly will be either in Greenwood, 15 miles south of Indianapolis, or in Fort Wayne. Both would be completed next year. The design crisscrosses opposing lanes to allow cars to enter the highway without turning left in front of oncoming traffic.
Missouri, Georgia, Maryland, Utah, Tennessee, Kentucky and New York already are using the traffic patterns. In Missouri, which began using the design in Springfield in 2009, officials credit it for helping to reduce crashes. A six-month study of a diverging diamond interchange in St. Louis showed a 38 percent drop in crashes and no wrong-way crashes. Meanwhile, the overall traffic flow quadrupled.
“It’s very normal and natural because you’re following the flow of the road,” said KimberLee Peters, an engineer with the Indiana Department of Transportation. “When you drive it, you may not even realize that traffic has shifted.”
The proposal is to install the diverging diamond at Worthsville Road in Greenwood at an entrance to Interstate 65. Greenwood leaders think adding a new interchange there will spur business and commercial growth. They also hope it will ease traffic at other highway ramps in Johnson County.
Greenwood leaders have agreed to pay for half of the up to $22 million project, while the state would pay for the rest.
Engineers believe the design is the best option for Worthsville Road, but two other designs also are being considered. INDOT plans to hold public meetings before making a decision.
Greenwood Mayor Mark Myers said the diverging diamond could save the city about $3 million.
“It’s hard to argue against this one,” Myers said. “I think it’s a great idea.”
He said it also leaves for walkers and bike riders on a path that runs in the center of both traffic lanes.
“It helps with our trail system,” Myers said.
Some motorists remain leery, though.
“I don’t like it at all,” said Terri Pender, 31, who lives near the proposed interchange in Greenwood.
The state is paying $1.7 million for the Fort Wayne diverging diamond interchange. Other designs being considered would have cost $3 million to $6 million, INDOT engineer Susan Doell said. The interchange will end frequent traffic backups in a high-traffic area near hospitals and a movie theater in Fort Wayne, Doell said.
“The downside is it’s something new,” Doell said. “People are going to have to get used to it.”