emergency brake
US /ɪˈmɜːr.dʒən.si breɪk/
UK /ɪˈmɜːr.dʒən.si breɪk/

1.
a brake in a vehicle that can be used to stop it if the foot brake fails, or to prevent it from rolling when parked
:
•
Always engage the emergency brake when parking on a hill.
•
The driver pulled the emergency brake to avoid a collision.