Parking Brake Use Study 2013-01-0199

In the United States most passenger vehicles have an automatic transmission with a transmission shifter position labeled Park. When the transmission shift selector is placed in Park, a parking pawl (a pivotally mounted arm) engages a parking gear on the output shaft to immobilize the drive shaft and prevent the vehicle from moving. The driver also has the option of engaging the parking brake with a lever, pedal, or button to immobilize the vehicle. Many state driver's license manuals and vehicle owner's manuals commonly suggest the use of the parking brake every time the driver exits the vehicle regardless of the transmission type. Testing is performed by vehicle manufacturers on the automatic transmission to insure the Park shift position pawl holds the vehicle on steep slopes. This study was conducted to investigate how often and why drivers use the parking brake. Utilizing two survey techniques, the results and analysis show that a majority of drivers with vehicles equipped with automatic transmissions rarely if ever set their parking brake. Driver's typically place the transmission in Park and rely on the transmission to hold the vehicle after they park. The lack of use of the parking brake and the requirement for its use illustrates an industry problem not documented in literature.