My friend was asked whether he wanted to travel home with his colleagues on the train and he responded:
Nein, fahrt schon mal vor!
I know that vorfahren is a separable verb to mean "to ride along" but when I looked at the definition of "schon mal" or "schon einmal" I found it meant "ever / before / already" which made no sense.
Is there a reasonable definition of "schon mal"?