Determination of the Optimal Deceleration Lane Lengths for Two-Lane Exits Considering Operational Effects

This study aims to examine the deceleration lane lengths on operational effects by two-lane exits and present the optimal design length under different combinations of traffic and geometric conditions. Traffic simulation results indicate that it is benefit to use the longer deceleration lane length to minimize the impact of exiting traffic on the through movement vehicles. A maximal of 18.2 % reduction of the delay is obtained under the exiting volume of 2000 vph by replacing the 100 ft long deceleration lane with 1000 ft at the design speed of 55 mph. A minimal distance of 400 ft and 500 ft was recommended at the design speeds of 55 mph and 60 mph. At the design speeds of 65 mph and 70 mph, a deceleration lane was recommended to be loner than 600 ft. Since there is no clear standard of the minimal deceleration lane length for the two-lane exit, the results from this study could be used as a design guideline for the two-lane exits.