Photo Ticketing System Evaluation
This site hosts independent research on the performance of photo ticketing systems in Arizona. The purported reason for employing photo ticketing is to improve safety — measured by the number of crashes, and the number of injury and fatality crashes. A system that does not reduce total crashes, or injury and fatality crashes, does not improve safety.
Many municipalities judge photo ticketing with a simple police tally of crashes before and after installation. That approach ignores statistical bias and the other factors that affect crash counts at a given location:
Selection bias
Locations chosen for enforcement usually have an above-average crash count. Often that spike is temporary and would revert toward the average on its own — a reversion-to-the-mean effect that's easy to mistake for camera performance.
Traffic volume
Crashes correlate with miles driven — more traffic, more crashes. Arizona's statewide mileage declined from 2008–2013, the same window in which many camera systems went live. That decline, not the cameras, explains much of the reduction municipalities have claimed credit for.
Regional & national trends
Safer vehicles, higher seatbelt use, and stricter drunk-driving enforcement all move crash and fatality numbers independent of any local camera program.
Control intersections
A properly evaluated intersection should be compared against a similar, unmonitored one — not judged against its own before/after numbers in isolation.
Using ADOT's statewide crash database and mileage figures, this research compares individual intersections against city and statewide trends over a ten-year period. A genuine safety improvement would show up as a clear divergence from those trends — and consistently, it doesn't.
Due to the limitations of being an independent citizen researcher, this analysis doesn't implement every safeguard above — but it's more rigorous than the simple before/after tallies municipalities typically publish.