Integrating Feedback into the Transportation Planning Model

Abstract

This research develops and applies a new structure for the transportation planning model that includes feedback between demand, assignment, and traffic control. New methods, combined with a renewed interest in transportation planning models prompted by the Clean Air Act of 1990 and the Intermodal Surface Transportation Efficiency Act of 1991, warrant a reconsideration of the traditional "four-step" transportation planning model. This paper presents an algorithm for feedback which results in consistent travel times as input to travel demand and output from route assignment. The model, including six stages of Trip Generation, Destination Choice, Mode Choice, Departure Time Choice, Route Assignment and Intersection Control is briefly outlined. This is followed by an application comparing a base year 1990 application with a forecast year of 2010. The 2010 forecast is solved both with and without feedback for comparison purposes. Incorporation of feedback gives significantly different results than the standard model.