Freeway management systems and motor vehicle crashes: a case study of Phoenix, Arizona.
This paper measures the impact of a freeway management system (FMS) on the incidence of reported motor vehicle crashes in Phoenix, AZ. Using a fixed effects negative binomial regression model, I find that the FMS reduces the frequency of crashes involving property damage only, possible injury, and minor injury by 25, 30, and 21%, respectively. I find no evidence for an effect on the frequency of major injury crashes or fatal crashes, although such accidents account for less than 5% of the total crashes in Phoenix. Classifying the data by the type of crash rather than by severity, I find that the frequencies of rearend crashes and sideswipe crashes are reduced by 25 and 37%, respectively, and I find no evidence of an effect on single vehicle crashes. The results are robust to many different model specifications, including a variety of functional forms, covariates, and data. A conservative estimate of the annual crash benefits of the FMS in Phoenix ranges from $4.8-13.2 million, depending on various assumptions about the value of pain and suffering and about the extent of crash underreporting. These annual crash benefits far outweigh the $1.6 million in annual operating and maintenance costs of the Phoenix FMS, and they offset considerably the approximately $47 million invested to date in the design and construction of the system.
Olmstead
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John F. Kennedy School of Government, Harvard University, Cambridge, MA 02138, USA. todd.olmstead@post.harvard.edu
D000063:Accidents, Traffic / Q000145:classification / Q000517:prevention & control* / Q000706:statistics & numerical data; D001130:Arizona / Q000453:epidemiology; D016022:Case-Control Studies; D003362:Cost-Benefit Analysis; D006801:Humans; D015994:Incidence; D007256:Information Systems; D008962:Models, Theoretical; D019982:Organizational Case Studies; D012044:Regression Analysis; D017751:Safety Management / Q000458:organization & administration*; D014947:Wounds and Injuries / Q000453:epidemiology / Q000517:prevention & control