black construction danger erection protection red scaffold scaffolding sign warning warning sign blue car carpark cars child safety child safety warning sign children dehydration exhaustion heat heat stroke motor car motor vehicle safety vehicle white driving pictogram road sign Road Warning Sign snow snow ahead snow sign snowing traffic traffic sign winter alert care concern Dirt dirty elephant elephants jungle jungle track sign old old sign rules signs yellow advice appropriate behavior appropriate behaviour directions no entry prohibited prohibition rust rusty unwanted weathered appropriate-behavior appropriate-behaviour background caution close-up colors colours communication dangerous distinctive external greenery hazard hazardous hazardous-pathway message path-warning-sign shade shadows signage sunlight tree trees trip-warning tripping-up uneven vegetation walking-hazard warning-sign prevent prevention protect risk risk area risky safeguard security theft risk canada signpost tsunami zone emergencies emergency barrier cliff crumble drop edge England fall fence hole pit post quarry sand cliff sandstone work works dangers law legalities