Transportation planners and engineers must often work together to forecast future changes in travel demand resulting from alterations in the roadway system, land-use patterns, and demographic characteristics. Unfortunately, conventional planning and operational analysis procedures fail to recognize the interdependent relationship between forecasted travel demand and intersection-level traffic control. Most planning models, for example, incorporate the impact of traffic congestion on travel forecasts through simplistic relationships between the basic number of through travel lanes and the assigned traffic demand. The impact of intersection traffic control is generally not considered or is included as a fixed penalty that is not sensitive to the assigned flow. Conversely, most operational analysis tools assume fixed patterns of traffic flow regardless of changes in intersection traffic control conditions. Traffic volumes following improvements such as the installation of a traffic signal, signal timing optimization, or the addition of an auxiliary turn lane are assumed to not fluctuate from pre-improvement levels even though the improvement may substantially improve travel-time on a particular path through the local roadway network. This report presents a framework for a combined approach to travel demand forecasting and intersection operational analysis by integrating TransCAD with Synchro. For travel demand forecasting, the suggested framework follows the method of successive averages to approximate a user equilibrium solution of traffic assignment with volume dependent turn penalties. While similar procedures have been implemented previously, the integration with Synchro breaks new ground to support detailed analysis of intersection operations including complex phasing schemes, coordinated systems, and stop-controlled intersections. For operational analysis, the suggested framework explicitly considers the potential redistribution of traffic patterns following implementation of a wide variety of intersection-level transportation enhancements.
Samenvatting