Traffic safety and the switch to a primary seat belt law: The California experience

David J. Houston, Lilliard E. Richardson

Research output: Contribution to journalArticlepeer-review

41 Scopus citations


This study explores whether the change of an existing seat belt law from secondary to primary enforcement enhances traffic safety. In particular, we examine traffic fatalities and injuries in California from 1988 to 1997. During the first half of this period, California law provided for secondary enforcement of its mandatory seat belt law, but in 1993 it upgraded the law to primary enforcement. Controlling for the number of motor vehicle collisions, a Box-Tiao intervention analysis of the time series is used to compare the monthly fatalities and injuries before and after the change in the enforcement provision. The results show that California experienced an improvement in traffic safety in terms of a significant reduction in injuries, but the change in enforcement provision had no statistically significant impact on fatalities.

Original languageEnglish (US)
Pages (from-to)743-751
Number of pages9
JournalAccident Analysis and Prevention
Issue number6
StatePublished - Nov 2002

All Science Journal Classification (ASJC) codes

  • Human Factors and Ergonomics
  • Safety, Risk, Reliability and Quality
  • Public Health, Environmental and Occupational Health


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