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Impact of automated photo enforcement of vehicle speed in school zones: interrupted time series analysis
  1. D Alex Quistberg1,2,
  2. Leah L Thompson3,
  3. James Curtin4,
  4. Frederick P Rivara1,3,5,6,
  5. Beth E Ebel1,3,5,6
  1. 1 Harborview Injury Prevention & Research Center, University of Washington, Seattle, Washington, USA
  2. 2 Department of Anesthesiology & Pain Medicine, University of Washington, Seattle, Washington, USA
  3. 3 Department of Pediatrics, University of Washington, Seattle, Washington, USA
  4. 4 Seattle Department of Transportation, City of Seattle, Seattle, Washington, USA
  5. 5 Seattle Children’s Research Institute, Seattle Children’s Hospital, Seattle, Washington, USA
  6. 6 Department of Epidemiology, University of Washington, Seattle, Washington, USA
  1. Correspondence to Dr D Alex Quistberg, Urban Health Collaborative, Drexel University, Philadelphia, PA 19104, USA; daq26{at}


Objective Measure the impact of automated photo speed enforcement in school zones on motorist speed and speeding violation rates during school travel.

Methods Automated enforcement cameras, active during school commuting hours, were installed around four elementary schools in Seattle, Washington, USA in 2012. We examined the effect of automated enforcement on motorist speeds and speed violation rates during the citation period (10 December 2012 to 15 January 2015) compared with the ‘warning’ period (1 November to 9 December 2012). We evaluated outcomes with an interrupted time series approach using multilevel mixed linear regression.

Results Motorist speed violation rates decreased by nearly half in the citation period compared with the warning period (standardised incident rate ratio 0.53, 95% CI 0.42 to 0.66). The hourly maximum violation speed and mean hourly speeds decreased 2.1 MPH (95% CI –2.88 to –1.39) and 1.1 MPH (95% CI –1.64 to – 0.60), respectively. The impact of automated enforcement was sustained during the second year of implementation.

Conclusion Automated photo enforcement of speed limit in school zones was effective at reducing motorist speed violations and also achieved a significant reduction in mean motorist speed.

  • school road safety
  • automated speed enforcement
  • interrupted time series
  • pedestrian safety

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  • Contributors DAQ, FPR and BEE conceived of and designed this study. DAQ, LLT, JC and BEE acquired the data. DAQ analysed the data. DAQ, LLT, FPR and BEE reviewed data analyses and interpreted the data. DAQ and LLT drafted the article. All authors revised the article for critically important intellectual content and approved of the final version for publication.

  • Funding Research reported in this article was supported by the Eunice Kennedy Shriver National Institute of Child Health and Human Development of the National Institutes of Health under award number T32HD057822.

  • Disclaimer The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

  • Competing interests None declared.

  • Patient consent Not required.

  • Ethics approval Institutional Review Board of the University of Washington.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement Data may be requested from American Traffic Solutions, Inc.

  • Author note The content is solely the responsibility of the authors and does not necessarily represent

    the official views of the National Institutes of Health.