Official Title: City of Seattle Traffic Safety Camera Pilot Project Evaluation Report
This is a 2007 report for the city of Seattle, Washington, USA on the effects of red-light cameras in the city of Seattle, Washington. This study compares the before and after crash statistics of 4 RLC intersections in that city. The study uses 40 months of pre-RLC crash data compared to 7 to 10 months of post-RLC data. The statistics used in this analysis are from the Seattle Police Department and the study does not define a fixed Distance-From-Intersection inclusion zone for crashes. This study uses crash data from 4 non-RLC intersections in the city as control data. There are no data or conclusions in this report that suggest a reduction or increase in fatalities due to RLCs. The results show that total crashes at RLC-equipped intersections have increased by 6% as well as a 30% decrease in injury crashes for the first 7 to 10 months after RLCs were installed at RLC intersections. The study concludes that : "There is little evidence that cameras have decreased the frequency of all auto crashes or of the more dangerous angle collisions; however, it does appear that cameras may have mitigated the severity of crashes".
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This is a brief 15 page report, there is no detail source data per intersection included in this report, and the pre-RC data used has several gaps of two months which somewhat reduces the validity of the report. Also, one of the four RLC intersections was only operational for 7 months at the time the report was written, but the difference in post-RLC data periods is not mentioned anywhere and that fact is not taken into account in the analysis of the report which also diminishes the validity of the report. The use of only 4 RLC intersections and 4 control intersections is far below the average for this kind of study and reduces the usefulness of the report. The before-RLC period is very long and the after-RLC period is well below average for this kind of study and somewhat reduces the validity of the conclusions. This report mentions that a final report will be issued later that year, but it is 3 years later and no report has ever been filed that we can determine. The conclusions are supported by the very limited data that is supplied in this report.