BACKGROUND

Mobility and safety are often identified in transportation agency mission statements as core values. State departments of transportation and local agencies are progressively incorporating the Safe System approach that works by building and reinforcing multiple layers of protection to prevent crashes from happening in the first place and minimize the harm caused to those involved when crashes do occur. At the same time, many operational changes are being implemented to reduce delays and improve traffic flow, some of which could have unintended negative effects on safety. The goals of safety and mobility must be balanced and better understood.

Roadway and intersection configurations, vehicle speed, and multimodal level of service are examples of metrics that can be used to understand operational improvements and help predict changes in crash outcomes. In addition, systemwide changes in factors related to use of the roadway network, such as land development, traffic volume, speed limit, and mode choice can affect the safety performance of the system and of individual facilities.

Studies of corridor and intersection operational improvements show mixed effects on safety outcomes, leaving agencies with an incomplete understanding of the relationship between operational changes and safety performance. Transportation agencies need tools to support decisions concerning tradeoffs between mobility, capacity, and crash severity. Providing a better understanding of these conflicts supports implementation of the Safe System approach.

OBJECTIVES

The objectives of this research are to develop a guide and an associated quantitative analysis procedure to improve the understanding of how operational changes in different design and developmental contexts can impact safety performance. Results of this research will provide transportation agencies and other practitioners with means to better understand anticipated safety implications associated with implementing changes operational changes.