United States Department of Transportation
i
Identification of core functions and development of a deployment planning tool for safety service patrols in Virginia.
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2006-01-01
[PDF-538.73 KB]
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Edition:Final report;4/15/200612/30/2006.
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Abstract:The purpose of this study was to identify and document the core functions of the Virginia Department of Transportation's (VDOT) Safety Service Patrol (SSP) programs and to develop a deployment planning tool that would help VDOT decision-makers when considering expanding SSP coverage and/or altering existing route coverage. The study involved a literature review of the functions, mission statements, objectives, and deployment criteria of other SSP programs across the United States that are commonly accepted as successful; documentation of the functions currently provided by VDOT's SSP programs and the benefit each provides; and the development of an SSP deployment planning tool. VDOT's SSP programs share core functions, but the urban and rural programs differ in the type of benefits they emphasize. Urban regions place greater emphasis on the benefits associated with reduced travel delays and number of secondary crashes, and rural regions place greater emphasis on the benefits associated with improved safety for motorists in distress and creation of goodwill for VDOT. The study recommends that VDOT's regional operations directors prioritize the core functions of their programs in relation to the direct, indirect, and incidental benefits each provides. Emphasis should be placed on those core functions that provide the most direct benefits. Indirect and incidental benefits are also of importance and should not be overlooked in the prioritization process. The planning tool developed in this study is a segment-based ranking scheme that can be applied to rural and urban freeway segments. Within the tool an incident prediction model was developed to predict incidents statistically using freeway segment average annual daily traffic (AADT), length, average daily percent of ADT served, and truck percentage. The study recommends that the SSP deployment planning tool be used by VDOT's regional operations directors as they consider deploying new patrols or altering existing ones. To do this, existing and potential SSP routes should be included in the evaluation. Each route must be divided into its constituent segments (traffic links), and each segment scored using the predicted number of incidents, level of service, planned projects, air quality, maximum access distance, maximum structure length, AADT, and daily truck volume. Routes should then be ranked based on their scores. Hypothetically, if three routes (X, Y, and Z) are under consideration for SSP deployment in an urban region and funding is made available for only one deployment, the planning tool will indicate the route that will provide the greatest return on investment. For example, if the annual costs of operating an SSP on a route are $275,000 and if routes X, Y, and Z have benefit/cost ratios of 4.8, 4.3, and 3.1, respectively, the benefits to VDOT of choosing route X over route Y or Z are $137,500 and $467,500, respectively.
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