Published in 2008
The Virginia Department of Transportation may be asked to consider proposed transportation projects that have not originated within the transportation planning process. Examples include offers by the private sector to build infrastructure in exchange for permission to develop land, advocacy by a regional government to add an interchange to a National Highway System route to encourage economic growth, a city's plan to narrow an arterial facility to increase community cohesion, and a county's request for pedestrian crossings on a high-speed arterial facility. This report refers to these proposals as stand-alone projects. In the short term, stand-alone projects may have significant merit as they can result in the provision of additional infrastructure or improved relations between state and local stakeholders. In the long term, they may not be beneficial if they result in adverse safety or operational consequences for the overall transportation system. Stand-alone proposals are difficult to evaluate because they lack detailed data, have not been studied as part of a region's planning process, require a relatively short response time, and are not discussed in the literature. This report describes stand-alone projects that have been proposed in Virginia, describes a methodology for evaluating them, and applies the methodology to two such projects: (1) a developer's proposal to provide additional infrastructure as part of a desired rezoning, and (2) a county's request to accommodate pedestrians on a 45-mph arterial facility bisecting residential and commercial development. Application of the methodology yielded the advantages and disadvantages for each proposal. For example, although the first project will reduce mainline delay for one facility, it will increase queue delay on another, will preclude the construction of two interchanges, and will increase delay overall. Yet the methodology also reveals that there is not necessarily a best answer: although the second project showed that a pedestrian overpass could accommodate pedestrian crossings at a capital cost of $0.16 per pedestrian crossing (compared to a capital cost of less than $0.01 per crossing for a pedestrian phase at an existing signal), neither alternative ensured that pedestrian risk would be minimized because pedestrian compliance with traffic laws could not be forecast precisely given the data available. In such situations, the utility of the methodology is that it delineates aspects of the proposal that can be assessed with available data in contrast to those that require judgment by decision makers. Because the study found that stand-alone projects are more common than expected and that they may yield negative or positive results, the report recommends that the methodology developed in this study be considered where stand-alone projects are to be evaluated and no other planning process is applicable. Depending on the availability of data, the level of accuracy desired, and the ability of the analyst to select the most appropriate performance measures, the methodology requires roughly 40 person-hours and does not require specialized software.
Michelle M. Smith, Lester A. Hoel, Ph.D.
Last updated: November 24, 2023