You press the same button you used to get into the car.
On the Wii, you press "A" to get into the car, and "A" when you want to get out. If the car is in motion, it will bring it to a halt, and you will get out.
Dear DJ! I couldn't fully understand your answer. Look i didn't understand what do u mean by Wii? I press "space" to enter into the car but cannot get off by pressing "space". Please help.
"A Friend should always underestimate your virtues and an Enemy overestimate your faults" Don Corleone
"Keep Your Friends Close but your Enemies Closer" Don Corleone
"In Business, A Friend is no less than a Foe" Dawood Ibrahim Kaskar
