The objective of this study was to determine the effect of left turn penalties on the accuracy of traffic assignment results. The left turn penalty model used in the study allows the selective penalizing of left turns without penalizing right turns and through movements. The model was applied to 70 signalized intersections in the 1963 Lancaster, PA., street network, and traffic assignment runs were made with penalty values ranging from0 to 60 seconds. The accuracies of the assigned volumes were compared using statistical techniques. The results showed that assigned traffic volumes obtained with left turn penalties in the range of 10 to 40 seconds were as accurate or more accurate than those obtained with zero penalties. Left turn penalties had more of an impact on the results of paricular iterations than on average assigned volumes. The study results indicate that the application of selective left turn penalties in traffic assignment is a technique with the potential of significantly traffic assignment accuracy.
Abstract