Taxi drivers in British Columbia are exempt from wearing their seatbelts if they are travelling at less than 70 km/h. I have never understood why this exemption was necessary, particularly in light of the fact that doing so actually endangers their passengers.
No one in a vehicle that I drive is exempt from wearing their seatbelt and I have been able to convince my taxi driver to follow suit. My collision reconstruction experience made me well aware of what happens to people who fail to wear their seatbelts and are involved in a motor vehicle collision. I have seen front seats torn out of the floor by unbelted rear seat passengers as they faithfully followed Newton's first law of motion during a crash. These "backseat bullets" very likely contributed to the death of the passenger in the front seat in one case I investigated.
Similarly, during collisions that are not head on, unbelted vehicle occupants in any seating position become heavy projectiles capable of doing significant damage to themselves and others. During collisions seat belts keep the driver behind the wheel and more likely to be in control of the vehicle post crash. They may still be able to steer and brake, perhaps keeping you out of a second crash in the oncoming lane or with roadside objects or other road users.
When I entered the cab, I simply told the driver that I would appreciate it if he wore his seatbelt. His response was that he was exempt and he made no move to put it on as he pulled away from the curb. My next step was to ask him politely to pull over and let me out. I would find a cab driver willing to wear his seatbelt while he drove me to my destination.
My driver was not happy, but put on his seatbelt. I felt safer for both of us.