Research into the most effective colour for warning lights on emergency vehicles = Efficacité des feux de signalisation colorés sur les véhicules de secours = Untersuchung von Farbeigenschaften für Warnlichter auf Notrettungsfahrzeugen.

The sensitivity of the eyes for combinations of red or blue filters with halogen bulbs during daylight and the hours of darkness are discussed. A large number of factors speak for the use of red identification lights on motor vehicles with special privileges in road traffic. All emergency vehicles ought to have two warning headlights. Sweden, however, decided to introduce blue identification lights.