The Malteser Hilfsdienst (MHD, German Order of Malta Ambulance) in Hamburg operates professional as well as volunteer services, using a variety of vehicles.
Krankentransportwagen – Ambulances
Rettungswagen – Emergency Ambulances
4-Tragen-Krankentransportwagen (KTW) – Civil Defence Ambulance (Four Stretchers)
This was actually used by the MHD, no specific markings and a generic “red cross” identification light are very confusing:
Sanitätsgruppenkraftwagen (SanGrKW) – Civil Defence Multi-Purpose Vehicle with Possible Ambulance Use
Behindertentransportwagen (BTW) – Wheelchair Ambulance
Mannschaftswagen (MTW) – Personnel Carrier
Personenwagen (PKW) – Utility Car
Please note that these are scans of old 35mm slides from my archives, with resultant deterioration in colours and sharpness.