An Analysis of VDOT's Sight Distance Requirements Relative to Context-Sensitive Designs

About the project:

Although the Virginia Department of Transportation’s intersection sight distance (ISD) requirements are intended to improve safety by maximizing visibility at intersections, these guidelines may not be reflected in practice in urban areas. Even where speeds are low, sight distance requirements can discourage or preclude elements of the urban streetscape such as street trees, on-street parking, and infrastructure such as shelters at bus stops. Some research suggests that by restricting more compact urban intersection forms, high sight distances may actually result in higher auto speeds. This issue is particularly likely to arise in dense urban areas, including historic cores and new areas of traditional neighborhood developments. 

While data on the safety impacts of ISD is plentiful, little of it is tailored to address dense, low-speed urban environments. To fill this gap, VDOT seeks to compare crash impacts of ISD in urban environments of interest to calculations based on rural and suburban data, as well as crash modification factors found in industry publications. Furthermore, VDOT is interested in studying the safety outcomes of low-speed urban intersections where ISD requirements are not currently met. Finally, VDOT seeks to understand best practices for maintaining the intentional character of these urban areas while ensuring that sight distance does not become an issue.

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