"Taxi drivers are over 20 times more likely to be murdered on the job than other workers. By recognizing the hazards that lead to violent incidents and using proven prevention and control measures, employers and drivers can create safer working conditions. The Bureau of Labor Statistics' (BLS) data indicates that annual homicide rates for taxi drivers (and chauffeurs) from1998 to 2007 ranged from 9 per 100,000 workers, to 19. During that period the rate for all workers was at or below 0.5 per 100,000 workers. In other words, taxi drivers' homicide rates were between 21 and 33 times higher than the national average for all workers. […] Reducing risks requires employers and/or taxi drivers to assess their potential hazards and consider physical and procedural methods for reducing them. Generally, physical or 'engineering' controls should be considered first since they create physical barriers between drivers and the hazards. Procedural methods require changes in behavior, such as not accepting cash, to reduce risks."
United States. Occupational Safety and Health Administration: http://www.osha.gov/