I was just thinking I would recommend an indicator light on your dashboard somewhere. Put it where it won't reflect off the windshield at night and obscure your vision. Look for one that isn't too bright, either, or your face can reflect in the windshield (at least one poster here would like that
). Or, if your dash lights are on a dimmer switch, you could add another relay for it, and power the indicator light from the dash lights circuit; but that could interfere with a main reason to add the light in the first place: to help you remember the lights are switched manually "on" when you park and leave the bus in the daytime.