The city of Charleston tested a plan to improve the flow of traffic at the heavily congested intersection of Maybank Highway and River Road on Johns Island by keeping the light green a little longer, but it didn’t work.

Traffic snarls at the intersection every evening as vehicles back up onto the bridge over the Stono River. The problem is so severe that some people call it the “bottleneck bridge.”

Charleston County Councilman Joe Qualey pitched the idea of changing the lights to the city of Charleston, in which the intersection lies. Hernan Pena, the city’s director of traffic and transportation, doubted from the start that the plan would work, but he agreed to give it a try.

In a letter to Qualey, Pena said the plan failed to improve the flow of traffic largely because the choke point lies at the foot of the Paul J. Gelegotis Bridge across the Stono River, where two lanes on the bridge narrow to one on Maybank Highway. That’s about a mile from the intersection.

Qualey said the plan was worth exploring, and it didn’t cost anything.

Reach Diane Knich at 937-5491 or on Twitter @dianeknich.