art
barrier
boundary
caution
closed
construction
contour
control
cross
crossroad
danger
equipment
forbidden
gate
graphic
icon
illustration
isolated
light
line
linear
lineart
object
obstacle
open
outline
pattern
protection
rail
railing
railroad
railway
road
safety
seamless
sign
signal
stop
street
striped
symbol
track
traffic
train
transport
transportation
travel
vehicle
warning