On the crossing of the Connecticut River, I-95/US 1 comes into Old Lyme, New London County and immediately narrows to three southbound lanes, as it reaches the interchange with Route 156, where US 1 exits the highway and the concurrency ends. The freeway reduces to four lanes and heads into a heavily forested area with little development around the highway, where it crosses the Duck River. The road crosses the Threemile River prior to crossing the Fourmile River, as it enters the town of East Lyme. I-95 immediately comes to a trumpet interchange with the Rocky Neck Connector, that provides access to the Rocky Neck State Park. Continuing northeast through the center of East Lyme, the freeway enters into areas of mixed development with suburban elements before crossing the Pattagansett River within its interchange with Route 161, in the village of Flanders. Shorty afterward, there is an interchange with US 1, and the road crosses the Niantic River just before meeting the southern terminus of I-395. Here, the Connecticut Turnpike splits to the northeast along I-395, which heads toward Worcester, Massachusetts.