advisory
alert
announce
background
beware
caution
command
concept
constraint
curb
danger
dangerous
direction
green
info
information
informative
intelligent
isolated
label
orange
post
precaution
proceed
proceed with caution
prohibition
recommend
recommendation
red
restrict
restriction
road
rule
safety
sign
signal
sky
slow
slow down
slowly
stop
street
symbol
traffic
transportation
violation
warning
white
yellow