Turn Lane Lengths for Various Speed Roads and Evaluation of Determining Criteria

The purpose of this research project performed for The Minnesota Department of Transportation is to find the optimal length of right and left turn lanes at intersections from a system design point of view. This research project will also determine and quantify the influence of the factors that need to be considered when estimating turn lengths on specific type of intersection. The following parameters that possibly affect right and left turn lane lengths in Signalized and Unsignalized intersections are investigated in this study: speed, grade, through and turning traffic volumes, heavy vehicle mixture, and protected/unprotected left and right turn signalization. In this study, there is also an in depth review of technical literature and a national and international survey of turn lane design practices. The videotaped observational data was used to calibrate a computer model of the intersection scenarios that were video taped using traffic analysis software SYNCHRO and SimTraffic. The calibrated computer models were then used to conduct a sensitivity analysis to determine the factors that could be used to predict the most optimal turn lane length. Our major challenge was to develop a set of equations that accurately predicts the queue length of the turning traffic at the standard intersection types.