Partners in Crime Prevention
Your agency may want to conduct training seminars designed to educate drivers as to how they can avoid being victimized.
Some assaultive behavior can be traced to the conduct of the drivers themselves. Overcharging and taking the longest way possible is almost sure to elicit a negative passenger response. And, yes, some taxi drivers are just plain nasty people who are nasty to their customers. You may want to educate them on a version of verbal judo and help them see that treating their customers better will make them safer.
Drivers should also be trained not to chase fare evaders. An unarmed driver with no portable radio chasing an unknown suspect in an unknown area with little chance of police response is a bad scenario.
Your agency can also persuade the taxi companies to institute a policy that requires the dispatcher to confirm the fare with a call back number, be it a residence, business, or cell phone number. Also, the driver and dispatch can establish a secret code that allows the driver to surreptitiously advise of a potentially troublesome passenger.