The intersection of U.S. 31 and Thompson Road on the south side of Indianapolis opened on Oct. 8 as the state’s first displaced left turn (DLT) intersection.
Previously, the southside Indianapolis intersection was a meeting point of a six-lane highway and five-lane major road with just one sidewalk.
With DLTs, all left turns from the mainline road, and in some cases left turns from the minor roadway, are made in a two-stage process. Vehicles cross to the opposite side of the roadway at an upstream secondary signalized intersection, and then proceed to the primary signalized intersection via a special roadway parallel to the mainline. At the primary signal, vehicles complete the left turn at the same time as through traffic because they are no longer in conflict with one another, due to the upstream crossover intersections. Traffic movements are controlled by traffic signals.
Traffic safety is improved because motorists no longer must navigate left turns inside the intersection. DLTs reduce delay at high-volume locations by enabling left-turning traffic and through traffic to proceed through the main intersection simultaneously.
For the Indianapolis project, the DLT was applied to northbound and southbound traffic on U.S. 31. Crews reconstructed the medians, repainted lines, built additional right-turn lanes for traffic turning onto U.S. 31, and added a traffic signal to the I-465 eastbound exit ramp onto U.S. 31.
INDOT Senior Project Manager Christie Williams said: “The new configuration eliminates one phase of signaling, therefore enabling more traffic to flow through the interchange. Also, southbound U.S. 31 traffic now is stopped at a light, and only the motorists using the left-turn crossover lane will be turning left. Before this project, motorists were at someone’s mercy to let them all the way over to the left.”