Despite numerous ITS deployments in work zones a framework for evaluating the

Despite numerous its deployments in work zones a

This preview shows page 13 - 15 out of 71 pages.

incidents. Despite numerous ITS deployments in work zones, a framework for evaluating the effectiveness of these deployments does not exist. To justify the continued development and implementation of ITS in work zones, there is a need to develop a uniform framework to determine the ITS effectiveness for specific work zone projects. In addition, guidance on the circumstances under which ITS deployment is recommended for a work zone is beneficial to agencies. Such a framework is developed in this report. The framework consists of four steps as shown in Figure E1. In the first step, criteria for selecting work zone sites for ITS deployment are established. The second step consists of selecting operational and safety performance measures for evaluating a deployment. Data needs for measuring and estimating the chosen measures are then determined. The performance benefits are quantified, total costs of ITS deployment estimated, and the benefit-cost ratio is computed in the fourth step. Figure E1. Work zone ITS evaluation framework The site selection criteria for choosing work zones that offer the greatest potential for traffic and safety improvement through ITS deployment is presented in Figure E2. They are: frequent congestion, high traffic impact at the work zone, availability of alternative routes and over-capacity demand. Depending on the goals of the deployed ITS, one or more of the following five performance measures is recommended: delay, diversion rate, queue length, crash frequency, and speed. These measures were obtained from the synthesis of the existing literature on ITS deployment studies. Using the same measures across ITS deployments will allow for an easier comparison of the results. Traffic sensors that collect traffic flow, speed, and occupancy are key to the chosen performance measures. Additional equipment such as temporary detectors and queue detection trailers may also be needed for accurately measuring queue length. For example, diversion rates can be computed using traffic flow data collected from temporary traffic sensors deployed on the mainline and ramp. Crash data collected by the law enforcement agencies are typically archived by the state DOT. Even though benefit-cost methodology has been implemented in other transportation areas, the application to work zone ITS involves additional wrinkles such as the need to include technology cost factors and the computation of dynamic road user costs. Site selection Performance measures selection Data collection Benefit-cost analysis Operational measures (Delay, Diversion, Queue length) Safety measures (Crashes, Speed-based measures)
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xii Figure E2. Site characteristics warranting ITS deployment The proposed work zone ITS deployment framework is illustrated using two case studies.
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