Student Researcher: Thareth Yin

Faculty Advisor: C. Monsere

ABSTRACT: In 2001, the Oregon Department of Transportation (ODOT) reduced illumination at select locations on Oregon interstate highways in response to a Governor's directive to conserve power. The illumination reduction occurred for various interchanges and highway sections between October 2001 and March 2002. The research establishes a baseline comparison using the simple before-after method of evaluation to determine if there were any significant changes in overall safety at the locations with reduced illumination and makes recommendations on future modeling efforts. The simple before-after study used ODOT crash data to test five study designs with varying 'before' and 'after' periods. No control sites of volumes were used in this preliminary analysis. The 'before' period ranged from 1 year to 5 years of data and the 'after' period ranged from 1 year to 2 years. It was found that only two study designs produced statistically reliable results. These were the designs with 5 years before and 2 years after and with 3 years before and 2 years after data. Both study designs show that an increase in crashes at the project locations and it was estimated to be between 7 percent and 22 percent with a statistical significance of 95 percent. While these results are an indication that crash frequencies have increased at the project locations during the study period; it cannot conclusively determine what relationship the illumination reduction had to the increase. Further research was done on crash modeling techniques to enhance the accuracy of the simple before-after study. Recommendations on model form, parameter selection, and variables are discussed.

PRODUCTS:

thesis Yin, Thareth, "Effects of Highway Illumination Reduction on Highway Safety Performance." M.S. Project, Department of Civil Environmental Engineering, Portland State University, 2005.

thesis proposal Yin, Thareth, "Effects of Highway Illumination Reduction on Highway Safety Performance." M.S. Project Proposal, Department of Civil Environmental Engineering, Portland State University, 2004.