|Motorcycle theft is the most common crime in Taiwan. It occupies more than half of the total police recorded crime from 1996 to 1999 .The purpose of this study is to examine the correlation between implementation of helmet law and motorcycle theft in Taiwan. Taiwan 's Helmet Law took effect on June 1,1997.
Monthly data on the number of motorcycle theft as well as number of helmet violations were obtained from Criminal Investigation Bureau of the National Police Administration. Data on the number of registered motorcycles were obtained from the Department of Communication
One sample t-test shows that there is a significant mean difference on the monthly number of motorcycle thefts between before and after the helmets law took effect. One-way ANOVA shows that city and counties with stronger police enforcement on helmet law also have a higher reduction in motorcycle thefts rates. There is also a significant negative Pearson correlation between police enforcement of helmet law and motorcycle thefts rates. That is, the stronger the police enforcement , the lower the motorcycle theft rate. ARIMA Intervention model shows that implementation of helmet law has a significant impact on the time series of motorcycle thefts in Taiwan.
ARIMA Transfer Function Model further shows that enforcement of helmet law is the leading factor on the reduction of motorcycle theft rate.
Data analyses also found that the decline of motorcycle theft rate does not increase other theft cases. On the contrary, the decline of motorcycle theft also has the benefit diffusion of lowering the robbery and stolen goods rates in Taiwan.
To sum up the above findings, implementation of helmet law is one of the factors for the decline of motorcycle theft in Taiwan. And Taiwan's experience further supports Felson and Clarke's(1998) Opportunity Theory.
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