Longitudinal rumble strips is a safety feature or treatment on a paved shoulder capable of alerting drivers that
their motor vehicle is departing the traveled lane. This treatment has proven to be effective specially preventing
roadway departure crashes.
In 2009, Puerto Rico started the implementation of longitudinal shoulder rumble strips on freeways. In 2010, the
Highway Safety Manual (HSM) provide tools for decision making to estimate how effective a countermeasure or
set of countermeasures will be in reducing crashes at a specific location. The Crash Modification Factors (CMF)
are used to quantify the effect of a particular treatment on expected crash frequency adjusting the estimate of
crash frequency from a base condition defined by a Safety Performance Function (SPF) to the specific conditions
present at a site. In the 2010 HSM, CMF’s for freeway applications using intermittent longitudinal rumble strips
on shoulders were not included.
This paper documents the process of developing CMF for intermittent rumble strips on freeway segments, in
rolling to mountainous topography and the development of SPF’s. The study area is PR-52, a 108.3 km toll
freeway facility, part of NHS originating in San Juan, crossing the central mountain range and ends in the city of
Ponce.
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