Systematic Evaluation of Run-Off-Road Crash Locations in Wisconsin
by Alex Drakopoulos and Ertan Örnek
Department of Civil and Environmental Engineering
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Systematic Evaluation of Run-Off-Road Crash Locations in Wisconsin
Abstract
In 2000 the Wisconsin Department of Transportation put forth a Strategic Highway Safety Plan, aligned with AASHTOrecommended
safety actions aiming to reduce nation-wide fatalities by 5-7 thousand per year. The present effort was
conceived within a state-wide action plan to keep vehicles on the roadway and minimize the consequences of leaving the
roadway; it also aimed to improve state-wide data and decision support systems. A method to systematically identify
crashes on undivided State Trunk Highways (STH) was developed; crash rates, crash densities (crashes/mile) and other
safety statistics were developed; a floating highway segment algorithm (
PRÈCIS) that can identify crash rates at any givenpoint along any undivided STH was also developed. Statistics were produced for two- three- and four-lane urban and rural
STH, with an emphasis on two-lane two-way rural undivided highways. 335,666 non-deer crashes were reported in the
state of Wisconsin between 1998 and 2000. 143,117 of those crashes occurred on STH, 60,345 of which occurred on 9,474
miles of undivided STH. Most of this mileage is rural (8900 miles), with the majority being two-lane highways (8820
miles). Crash rates, crash densities and other statistics were developed for the undivided parts of each STH, and each
number of lanes/population density (urban or rural) cohort. State-wide statistics were developed as well. Crash rates and
crash densities were developed for all, non-intersection, and Run-off-Road crashes. Similar crash statistics for Run-off-
Road crashes were calculated for injury & fatal, wet & snow, darkness, horizontal or vertical curve and fixed object crashes.
For Run-off-Road crashes on two-lane rural STH, statistics were developed for overturn, fixed object, ditch, tree, guardrail,
utility pole embankment and sign post crashes. Results of the floating highway segment algorithm
PRÈCIS were plotted ona GIS-based map; color-coded continuous lines parallel to a given STH alignment indicated crash the crash rate at any given
point along the STH; colored line charts accompanying the GIS map indicated crash rates at any mile point. The ability to
produce special tables listing highway features and crash information (Interleaf tables) sorted by mile point was also
provided. Two strategies for the identification of highway segments in need of safety improvements were provided.