Abstract: The present invention refers to a safety seat belt locking device for vehicles, comprising a relay with an adjustable time delay, a solenoid device connected to a locking-lever and an impact-responsive switch. If an impact occurs from any direction, which might endanger the passenger, the impact-responsive switch will cause current to be cut off to the solenoid device after a determined time delay, thus releasing the tongue of the safety belt automatically. This device is of particular interest where the car catches fire after a collision, or in similar circumstances, when the passenger should be able to leave the car as quickly as possible.