Keep tramways [American English: streetcar tracks] clear
This poster from 1967 by Amsterdam’s traffic police was designed by advertising agency Hou Maet, featuring an anthromorphic tram and Adrian Frutiger’s Univers in all-lowercase letters. Printed by Stadsdrukkerij Amsterdam.
Via Tim Boric’s Flickr photostream. Peter Eijkman recalls that these were also used as rear window decals. Henk Gralman has a photo from 1967 showing such an application. On the design with the red hands, he comments:
Some naughty and creative minds interpreted this as somebody being run over by a tram, which is somewhat the message, in a roundabout way. These notices could be seen on trams in Amsterdam and Rotterdam and some Belgium tram cities.