against circle letter mail mails many pictogram prohibition protest red road roadsign sign signs spam spammed stop warning advice alert appropriate-behavior appropriate-behaviour cars clearway communicate communication danger dangerous denied directions information informing keep-clear law legal no-parking no-standing no-temporary-parking not-allowed not-permitted permission-denied prohibited refusal restricted restriction restrictions risk risks risky road-safety road-side safety unacceptable vehicles warning-sign white access-denied asbestos avoid black care communicating concern damage demolition destruction fence fencing hazard hazardous health-risks keep-out mesh message no-access no-entry requirements unwanted caution parking announcement be-careful beware deep health polluted pollution protect protection rules toxic toxicity unhealthy water water-pollution water-toxicity weathered 3-D area attention banned cigarettes direction directive distinctive environment eye-catching glassy health-risk lettering location no-smoking plastic raised semi-transparent style surface surfaced surfaces surfacing symbol tactile texture textured textures thick thin wording words signage ban bus car clip embargo inhibition injunction interdict oval proscription round sphere suppression transport dig. digging tool