Except that the target may discover the leak, and the lack of ability to brake; newer cars will warn when the fluid pressure is low. Switching the car to first

Except that the target may discover the leak, and the lack of ability to brake; newer cars will warn when the fluid pressure is low. Switching the car to first gear to slow could get the driver out of immediate danger. I think the emergency brake uses a wire that is directly connected to the brakes. However, I do presume that the victim is paying attention to their vehicle and not in a sudden emergency condition.