Freight analysis and planning has lagged behind traditional transportation planning and is often neglected in models following the four-step process. National projections are that freight shipments will double in the next decade. In Alabama, manufacturing growth and increasing heavy vehicle usage will continue to strain already limited infrastructure. Freight focused planning and analysis tools are greatly needed. This research used a gravity distribution model and discrete event simulation to analyze growth scenarios and quantify congestion. The gravity distribution model develops a trip exchange matrix for freight using Alabama industry sector data. The matrix passes to a discrete event simulation software package incorporating time-of-day statistics and providing a visual communication tool for educating governing officials not involved in the transportation industry. The results of the combined system are the identification of congestion chokepoints and a listing of high priority capacity improvements needed to ensure the continued mobility of the infrastructure system.
Using a Gravity Distribution Model and Discrete Event Simulation to Enhance Freight Planning