TRB 2016 Blue Ribbon Committee
16th National Transportation Planning Applications Conference

Application of the Maryland Statewide Model – Applications of a Macro Based Capacity Constraint Assignment Technique

Corresponding Author: Scott Thompson-Graves, Whitman, Requardt, and Associates

Presented By: Scott Thompson-Graves, Whitman, Requardt & Associates, LLP


The Maryland State Highway Administration has developed several post processors and model applications to assist SHA in its planning and monitoring of the state highway system. Two applications were recently developed that are built upon a capacity constraint assignment technique developed within the macro assignment framework. This presentation will discuss the two applications of this technique and show how a simplified approach can provide similar benefits to more data intensive meso or micro assignments.

The first application is an Evacuation Model developed for SHA. The Model provides the user the opportunity to define both the evacuation area as well where the evacuees need to travel to along with other parameters including evacuation departure times, State of Emergency regions and factors for controlling the response rates and auto occupancy. The Evacuation Model uses a capacity constraint process to monitor those links where the volume exceeds the jam capacity. The trips using the link that are unserved in the current period are identified and distributed to the next period in the assignment. In the context of evacuation planning, this provides SHA the opportunity to test different evacuation scenarios and evaluate projects for their value in providing efficient evacuation.

A second application of the capacity constraint assignment is a project evaluation model developed to compare a low and high capacity network. The capacity constraint assignment technique is used to further evaluate the networks beyond the macro assignment differences to understand the projects ability to better serve demand in a corridor and reduce congestion levels. SHA intends to use this tool to measure the impacts of short term road closures and construction capacity reductions.

This presentation will present several case studies that were developed to test the ability of the models to provide Information for non-traditional planning such as determining the impacts and user costs of roadway construction, evaluating small and large scale evacuations, and determining roadway user benefits at the project and system-wide level.


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