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The Comparison Study on Observational Before-After Studies: Case Study on Safety Evaluation on Highways

관찰적 사전·사후 평가연구 방법의 비교 연구: 공용중인 고속도로 안전진단사업 효과평가를 사례로

  • Mun, Sung Ra (Graduate School of Environmental Studies, Seoul National University) ;
  • Lee, Young-Ihn (Graduate School of Environmental Studies, Seoul National University)
  • Received : 2013.08.30
  • Accepted : 2013.11.14
  • Published : 2013.12.31

Abstract

This study is to perform empirical analysis on observational before-after studies in Naive Method, Comparison Group(CG) Method and Empirical Bayes(EB) Method, and to compare with their results and to propose ways to apply to evaluation researches. For this purpose, the evaluation of road safety audit executed on Y$\breve{o}$ng-dong freeway in 2005 and 2006 was performed. As a result, all three methods have showed improved effects due to safety treatments. The safety effectiveness of Naive method is the largest, CG Method is the second and EB method is the last. The results of Naive method are overestimated due to the trend of reducing traffic accidents and those of CG method are affected by the external casual effects of comparison group. In the EB method, as "regression to the mean" phenomenon are controlled by reference group's accident model, it's result is relatively more accurate than that of other methods. In the conduct of evaluation studies, the analysts have to understand the pros and cons of each evaluation method. And after leading the survey on accident trends of related all sites, evaluation analysis is performed to be able to minimize bias.

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