Evaluation of the Scottsdale Loop 101 automated speed enforcement demonstration program

Shin, Kangwon, Washington, Simon P. and van Schalkwyk, Ida (2009) Evaluation of the Scottsdale Loop 101 automated speed enforcement demonstration program. Accident Analysis and Prevention, 41 3: 393-403. doi:10.1016/j.aap.2008.12.011

Author Shin, Kangwon
Washington, Simon P.
van Schalkwyk, Ida
Title Evaluation of the Scottsdale Loop 101 automated speed enforcement demonstration program
Journal name Accident Analysis and Prevention   Check publisher's open access policy
ISSN 0001-4575
Publication date 2009-05-01
Sub-type Article (original research)
DOI 10.1016/j.aap.2008.12.011
Open Access Status Not yet assessed
Volume 41
Issue 3
Start page 393
End page 403
Total pages 11
Place of publication Oxford, United Kingdom
Publisher Elsevier
Language eng
Abstract Speeding is recognized as a major contributing factor in traffic crashes. In order to reduce speed-related crashes, the city of Scottsdale, Arizona implemented the first fixed-camera photo speed enforcement program (SEP) on a limited access freeway in the US. The 9-month demonstration program spanning from January 2006 to October 2006 was implemented on a 6.5 mile urban freeway segment of Arizona State Route 101 running through Scottsdale. This paper presents the results of a comprehensive analysis of the impact of the SEP on speeding behavior, crashes, and the economic impact of crashes. The impact on speeding behavior was estimated using generalized least square estimation, in which the observed speeds and the speeding frequencies during the program period were compared to those during other periods. The impact of the SEP on crashes was estimated using 3 evaluation methods: a before-and-after (BA) analysis using a comparison group, a BA analysis with traffic flow correction, and an empirical Bayes BA analysis with time-variant safety. The analysis results reveal that speeding detection frequencies (speeds ≥ 76 mph) increased by a factor of 10.5 after the SEP was (temporarily) terminated. Average speeds in the enforcement zone were reduced by about 9 mph when the SEP was implemented, after accounting for the influence of traffic flow. All crash types were reduced except rear-end crashes, although the estimated magnitude of impact varies across estimation methods (and their corresponding assumptions). When considering Arizona-specific crash related injury costs, the SEP is estimated to yield about $17 million in annual safety benefits.
Keyword Automated speed enforcement
Empirical Bayes analysis
Freeway safety
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Civil Engineering Publications
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Created: Wed, 08 Mar 2017, 16:09:10 EST by Jeannette Watson on behalf of Learning and Research Services (UQ Library)