Two Lane Rural Road Safety Performance Functions

The objective of this research effort will be the development and implementation of state specific Safety Performance Functions (SPFs) for differing functional classes in Washington State. These SPFs will be used by all safety professionals and those responsible for safety assessment in Washington State. To achieve these objectives the following will occur: (1) an assessment of the current practice, (2) literature review of national and state practice, (3) development of SPFs by functional class, (4) development of SPFs implementation procedures for the differing tools and offices (e.g., HSM,, IHSDM, etc), and (5) recommendation for subsequent SPFs development. Considering the stated objective above, a systematic approach is necessary to address the substantial two-lane portion that is included in the 5,735 mile rural highway system in Washington State. Nearly 60% of this coverage involves minor and collector arterials, with an added proportion involving principal arterials as well. The research approach is tailored to account for informational demands in addressing this coverage, as well as computational needs required to develop a class of safety performance functions. The computational tools will involve both front-end performance formulas as well as Excel-based tools for the application of the formulas for estimating annual crash frequencies on two-lane rural highways.