Development of Safety Performance Functions for Network Screening or Roadway Departure Crashes in Virginia
Roadway departure (RD) is recognized as one of the eight emphasis areas in the Virginia 2017-2021 Strategic Highway Safety Plan (SHSP), and the Virginia Department of Transportation (VDOT) currently uses counts of RD crashes to identify locations for RD safety improvement. However, identifying locations based on crash counts is subject to bias and inaccuracy, leading to ineffective or erroneous outcomes. The safety performance functions (SPFs) VDOT has been using for statewide network screening might be used for RD safety improvement, but this could lead to undesirable outcomes in that the current SPFs focus on all crash types and RD safety issues are believed to be different from those of other crash types. This study was designed to develop SPFs for statewide network screening for RD safety improvements to overcome this issue. RD SPFs were developed
for 16 site types ranging from rural 2-lane segments to urban freeway segments with 8 or more lanes. It should be noted that crashes within 250 feet from an intersection are excluded according to VDOT’s RD definition.