crossing road road street roadsign sign signs warning advice alert appropriate behavior appropriate behaviour avoid black bright care concern danger dangerous denied directions not allowed not permitted permission denied prohibited prohibition protect protection rules safety warning sign yellow appropriate-behavior appropriate-behaviour be-careful below-ground careful caution communicating communication digging digging-dangers flammable gas gaseous natural-gas no-ignition pipeline pipes potential red risk risks risky stay-clear vapour vapours warned warning-sign white law legalities vehicle 2015 deny do not vector announcement beware camera cctv information informing lookout notice observation observe security surveillance under-observation video watch watched alcohol ban banned restricted restriction deep keep letters out prohibit signpost warn water wooden blue clouds san diego sky stop sign words