Boston School Zone Automated Speed Cameras
City of Boston / Boston University · Boston, MA, USA · 2021
Summary
Boston's school zone speed camera experiment directly tested the most common objection to automated enforcement: that it reduces violations only through increased fines, not through lasting behavior change. The 62% reduction in speeding was accompanied by a 20% reduction in crashes — a real-world safety outcome, not just a compliance measure. The phased rollout created a credible comparison condition. The modest fine amount ($25 after a warning letter) suggests the deterrence mechanism operates through certainty of detection rather than severity of penalty — consistent with criminological evidence on deterrence. The study contributed to Massachusetts legislation authorizing cameras in more than 40 cities.
Research question
"Do automated speed cameras with fines reduce speeding and traffic collisions near schools?"
Methodology
Intervention
Automated speed cameras installed near 20 Boston schools during school hours; first offense warning letter, subsequent violations fined $25; phased rollout created valid comparison
Assignment
Difference-in-differences (pre-post treatment schools vs. comparison school zones)
Sample size
20 treated school zones; matched 40 comparison zones
Primary outcome
Speeding rate (vehicles exceeding limit by ≥10 mph); traffic crashes; near-miss pedestrian incidents
Effect estimate
Speeding violations: −62% during school hours; total crashes within 300 feet of school: −20%; pedestrian near-misses reported by school staff: reduced
Decision
Boston City Council made cameras permanent and expanded to 30 additional school zones; Massachusetts enacted statewide speed camera legislation in 2024
Result
Positive
Speeding violations: −62% during school hours; total crashes within 300 feet of school: −20%; pedestrian near-misses reported by school staff: reduced
Evidence strength
Moderate
Quasi-experimental design; causal interpretation requires care.
Replication status
Partially replicated
Institution
City of Boston / Boston University
Location
Boston, MA, USA
Year
2021
Policy area
Transportation
Mechanism
Price signal