An Empirical Bayes before-after evaluation of road safety effects of a new motorway in Norway. (November 2017)

• Record Type: Journal Article
• Authors: Elvik, Rune; Ulstein, Heidi; Wifstad, Kristina; Syrstad, Ragnhild S.; Seeberg, Aase R.; Gulbrandsen, Magnus U.; Welde, Morten
• Is Part Of: Accident analysis and prevention. Volume 108(2017)
• Page Start: 285
• Page End: 296
• Publication Date: 2017-11
• Subjects: Motorway -- Road safety -- Empirical bayes -- Before-after; Accidents -- Prevention -- Periodicals; Accident Prevention -- Periodicals; Accidents -- Prévention -- Périodiques; 363.106
• DOI: 10.1016/j.aap.2017.09.014
• Languages: English
• ISSNs: 0001-4575

Abstract

Highlights: Few studies have evaluated the road safety effects of motorways. An Empirical Bayes before-after was made of a new motorway in Norway. The number of killed or seriously injured was reduced by about 75%. There were small changes in the number of injury accidents. Abstract: This paper presents an Empirical Bayes before-after evaluation of the road safety effects of a new motorway (freeway) in Østfold county, Norway. The before-period was 1996–2002. The after-period was 2009–2015. The road was rebuilt from an undivided two-lane road into a divided four-lane road. The number of killed or seriously injured road users was reduced by 75 percent, controlling for (downward) long-term trends and regression-to-the-mean (statistically significant at the 5 percent level; recorded numbers 71 before, 11 after). There were small changes in the number of injury accidents (185 before, 123 after; net effect −3%) and the number of slightly injured road users (403 before 279 after; net effect +5%). Motorways appear to mainly reduce injury severity, not the number of accidents. The paper discusses challenges in implementing the Empirical Bayes design when less than ideal data are available.