alert
approach
area
attention
barricade
barrier
block
border
boundary
car
caution
civil engineering
closed
construction
container
danger
direction
dusty
ed
forbidden
heed
hole
industrial
industry
keep
keep out
manufacturing
obstacle
outdoor
protection
road
safety
secured
sign
signal
silo
soil
stop
street
stripes
structure
symbol
terrain
trench
triangle
warn
work in progress
workplace
works
zone