A crash detection arrangement, to be installed in a motor vehicle, for detecting a crash and providing a control signal for controlling a safety device in the event that a crash is detected, the arrangement comprising an accelerometer and a control unit, the accelerometer being arranged to supply a signal to the control unit which is indicative of the acceleration of the vehicle, the control unit being adapted to: calculate a classification parameter based on the value of the signal from the accelerometer during a classification time period, which includes an interval of time before an initiation criterion was fulfilled; modify a crash evaluation algorithm in dependence upon the classification parameter; and perform the crash evaluation algorithm upon fulfillment of the initiation criterion to produce the control signal.