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University of Missouri

When the Wrong Way Is the Better Way

A new intersection design increases traffic flow by 30 percent.

Diverging diamond interchange

A diverging diamond interchange allows for more cars to move through during peak periods and doubles left-turn volume.

Wherever you drive in the United States, modes of organizing traffic — four-way stops, cloverleafs, express lanes — look functional and familiar. Only rarely does a better idea come along. But computer simulations by Praveen Edara, associate professor of civil engineering, show that a new interchange design, the diverging diamond, is worth a close look.

Missouri leads the nation with 15 of these novel interchanges in construction or use, including one in Columbia on the Stadium Boulevard bridge spanning Interstate 70.

Your first trip through a diverging diamond will be functional, if not familiar. It turns out that the word “diverging” is engineering-ese for crossing over to the left side of the road.

Compared to a standard diamond interchange, the design allows more cars through during peak periods and doubles left-turn volume. Achieving that in a standard interchange is costly, requiring widening the road to add lanes.

Edara is studying the safety of Missouri’s diverging diamond interchanges. After one year, data show a decrease in accidents at these sites, though final numbers are not yet available.