It's virtually impossible because of the centrifugal brakes that swing-out when the car starts falling fast. They are on every elevator car in the world,
AFAIK. The real danger in elevators is getting caught inside one when there is a fire and the car is stuck.
Saw an interesting show on Discovery or History channel not long ago about high-rise construction and how modern HR buildings only became possible when the elevator brake was invented. before that, no one would ride in an elevator.