I-10 eastbound through BR LA is a nightmare. It narrows down to 1 lane. Built that way.
You are correct, and I-10 eastbound that way runs through the Atchafalaya basin about 50 miles between Lafayette and Baton Rouge, not quite 1 lane but there is a bottleneck just on the other side of the MS River just pass the Bridge there near downtown Baton Rouge which is where all their State Government buildings are.