Rising gas prices: Effect on motorcyclist and bicyclist traffic deaths

Purpose: Gas prices have substantially risen and widely fluctuated in recent years. High gas prices tend to reduce motor vehicle travel and traffic deaths. High gas prices may also shift travel to fuel saving, yet riskier modes of transportation. The effect of rising gas prices on motorcyclist and bicyclist traffic deaths is estimated. Data and Method: The time series analysis separately examines national monthly motorcyclist and bicyclist death counts reported by FARS, 1994-12/20011 (n=216). The unobserved component models (UCM) include four deterministic predictors: (1) real average retail gasoline prices, (2) number of new building permits, (3) average surface temperatures, and (4) average precipitation amounts. UCM models allow stochastic representation of time series components (level, slope, season). Using SAS 9.3 software, the UCM models are estimated for 204 months (1/1994-12/2010), validated (1/2011-12/2011), and forecasted for 2012. Results: The analysis estimates that a $1 increase in real gasoline prices is followed by 34 more motorcyclist deaths (t=3.68; p <.001) the next month or about 408 per year. For bicyclists the corresponding estimate is 7 more deaths (t=2.68; p<.01) or about 84 per year. The final time series models fit the fatality counts well both within and out-of-sample (RSQadj.=.966 motorcyclists; RSQadj.=.729 for bicyclists). Model residuals conform to white noise properties. The final models predict well the substantial fluctuations in motorcyclist and bicyclist traffic deaths since 2008. Conclusion: Rising gasoline prices shift highway travel to more fuel saving transportation resulting in increased motorcyclist and bicyclist traffic deaths.