The Effectiveness of Taxi Partitions: The Baltimore Case

This report addresses the controversy concerning the effectiveness of taxi shields (partitions) by using case study and statistical analysis. It answers questions concerning whether or not shields reduce assaults on taxi drivers and by inference taxi driver homicides. Following a city-wide shield mandate in 1996 case study data show that for the City of Baltimore the percentage of shielded taxis rose from about 50% in 1995 to 100% in 1996 for the 1,151 licensed Baltimore cabs. Comparing the 12-month periods before and after the mandate the data shows that assaults on taxi drivers decreased 56%. Data also show that between the years 1991 when only 5% of the cabs had shields and 1997 when all did, assaults decreased 88%. Unless accounted for analytically, confounding factors such as annual changes in city crime rates, robberies, unemployment, and drug use could also contribute to the assault reduction. However, by comparing the assault rate for a shielded taxi association in 1991 with another similar, but unshielded, taxi association eliminates time varying confounding factors. This analysis shows that an unshielded Baltimore taxi driver in 1991 was five times more likely to experience assaults. Using linear regression to account for the time variation of the factors over the period 1991 to 1997, results indicate that reduced driver assaults correlated most highly with percentage taxis shielded. Average case study data, statistical tests and linear regressions show that assaults on taxi drivers are significantly related to shield installation. A related economic analysis yielded a 17-to-1 benefit-to-cost ratio of estimated savings from reduced injuries versus the costs of citywide shield installation. Thus, this study supports the use of shields in Baltimore for the case study licensed taxis. The results also argue for shields elsewhere, such as Baltimore County, and for other cities with conditions similar to those in Baltimore.