I've been working on a plugin on the German forums for a while now, and I think it's good enough now to post it here too.
In essence it provides players with a few new commands to control their vehicles:
Turn warning-, blue- and headlights on and off
Turn siren on and off (sadly it plays only once)
If you send a vehicle back to the base, all personnell it spawned with will first enter the vehicle (if possible). Patients and/or criminals get put in the vehicle too. Only w