How is the width of the continuous two-way center turn lane determined?
The AASHTO Policy on Geometric Design of Highways and Streets recommends 10 to 16-foot wide center turn lanes. The selection of a width within this range is based on an evaluation of vehicle speeds, vehicle types, roadside characteristics, and local conditions. For example: A 10 to 12 foot width would be considered for a residential road traveled at 25-30 mph, driven primarily by passenger vehicles, on level ground. A 12 to 14 foot width would be considered for speeds of 30-40 mph, with passenger cars and some trucks, on level terrain. Widths approaching 16 feet would be considered where there are large volumes of left-turning trucks. Based on a 45 mph posted speed, the number of large vehicles and trailers, and the rolling terrain, a 14-foot wide center turn lane is desirable. The Department will not consider any reductions in this width.
