Weakening Pennsylvania's motorcycle helmet law: Preliminary estimates

On September 5, 2003 the State of Pennsylvania exempted adult motorcyclist from wearing helmets provided they had passed a motorcycle safety course, or had been licensed for more than two years. The presentation reports preliminary estimates of the impact of the Pennsylvania's helmet law change. The Fatal Accident Reporting System (FARS) provides the quarterly data for the analysis spanning the decade, 1996 to 2005 (n=40). Three time series are examined: (1) motorcycle occupant deaths, (2) percent helmet use of motorcycle occupants involved in fatal crashes, and (3) motorcycle occupant deaths per 10,000 motorcycle registrations. The impact of the law change is estimated using multiple regression. The interrupted time series analysis captures seasonality by dummy variables. Helmet law change is measured by the proportion of time the universal helmet law was in effect in each quarter, and alternately, by reported helmet use in fatal crashes. The helmet law change is estimated to have reduced helmet use in fatal crashes by 30.5% points (CI 95%: 23.5%-37.5%) and increased motorcycle occupant deaths by 28.7% (CI 95%: 8.9%-44.3%). However, the impact on motorcycle occupant death rates is only 8.2% (CI 95%: -2.9%-19.2%) and marginally significant (p=.08, one tailed test). The helmet law repeal in Pennsylvania appears to have a less pronounced effect compared to other states. The likely reason is that helmet use in fatal crashes decreased less in Pennsylvania after law repeal than in other states. More post-repeal observations are needed to establish firmly the impact of Pennsylvania's helmet law repeal.