because I love you and I now happen to have a 172'd mk1 parked outside... here's a pic of the crash switch
all it is is an inertial switch which stops the signal wire from the ecu to the fuelpump/coilpack relay... car stops suddenly, fuel and ignition will be stopped!
if you don't want the switch, you can just bridge the wires.
I kept it as it seems a useful thing to have! my car is quite low and stiff and i've not yet had a problem with it cutting in unexpectedly either...