against circle letter mail mails many pictogram prohibition protest red road roadsign sign signs spam spammed stop warning bare barefoot foot no shoe shoes wear attention danger germany isolated safety traffic uneven road advice alert announcement appropriate-behavior appropriate-behaviour be-careful beware care careful carpark caution communicating communication concern dangerous directions informing Look looking lookout observant pedestrian pedestrian-speed reflective risk risks shared-area slow slow-down speed warning-sign watch watch-out white behave behavior behaviour black communicate information large-vehicles limitations limited restricted restriction restrictions reversal reversing risky trucks vehicles circles denied disapproval disapproved inform message messages not-allowed not-permitted permission-denied pictograms prohibited prohibitions protect protection public rules signage symbols don't go past this sign forbidden not beyond this point pedestrians stop here traffic sign advising be-prepared-to-stop cars hazard limited-access motorcars no-overtaking no-passing readiness ready road-sign roadwork workers workmen cycling incline slope steep track safeguard security theft risk