Date of Award

2000

Degree Type

Thesis

Degree Name

Master of Science in Civil and Environmental Engineering

Specialization

Civil Engineering

Department

Civil and Environmental Engineering

First Advisor

K. Wayne Lee

Abstract

Throughout the United States metropolitan area freeways are operating at or near capacity. Any disturbance in the traffic flow on these freeways, planned or unplanned, can result in varying degrees of congestion. Incident management programs have been established in urban areas nationwide to help reduce the magnitude of incident induced congestion. These programs focus mainly on the incident identification and response stage, and have only recently begun to develop the tools and techniques needed to manage the recovery stage. One technique that has been becoming more widely employed, with the increased focus incident management and overall traffic systems management, is alternate route traffic diversion. However, even when diversion strategies are employed, often only the main line freeway is evaluated and insufficient consideration is given to the effect of the diversion on the alternate route. Also, traffic diversion strategies are typically deployed only during extreme incidents and are seldom deployed or even analyzed for how they would help mitigate congestion related to minor traffic incidents. If delay on the freeway network as a whole is to be minimized, incident management programs need to incorporate comprehensive traffic management strategies and decision aids for the defining of traffic diversion strategies.

This study utilized Federal Highway Administration's (FHWA) traffic microsimulation software, CORSIM, to evaluate a freeway route diversion strategy that would increase traveler safety and alleviate congestion caused by minor incidents. The goal of the project was to reduce the impacts of minor incidents on a freeway system through the use of a methodically analyzed diversion strategy. The four specific objectives of the research were (1) to determine the impact of varying degrees of traffic diversion will have on the network evaluators for varying levels of traffic volumes encountering different incident situations; (2) to evaluate CORSIM and companion software as tools for performing this analysis; (3) to determine and document the procedure of the use of CORSIM in this facility; and ( 4) to recommend a diversion practice. The research analysis used typical measures of effectiveness to evaluate the effects of minor incidents and traffic diversion on a mainline and alternate route.

The results of the research show that CORSIM is a valuable tool for researchers, planners, or transportation engineers performing diversion strategy analysis. By utilizing CORSIM to simulate specific route diversion strategies valuable insights were gained into the effects that minor unplanned traffic incidents and deployed route diversion strategies will have on average network measures of effectiveness. It was found that the traffic condition the network is experiencing at the time of a minor incident and route diversion has distinct impacts on the network evaluators. CORSIM simulations demonstrated that the four levels of traffic condition tested produce distinct route diversion strategy recommendations. It was shown that the diversion modeled had a negative impact under AM peak traffic conditions, a slightly positive impact under 3/4 AM peak traffic conditions, significantly positive impact under 2/3 AM peak traffic conditions, and no impact under 1/2 AM peak traffic conditions. The significance of these results is that they indicate that it is only beneficial to the entire network to divert traffic for certain incident situations when the network is operating at 3/4 AM peak or 2/3 AM peak traffic. At AM peak and 1/2 AM peak traffic condition, diversion was not found to be warranted for any of the minor incident situations modeled.

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