caution
conceptual
control
controller
cross
crossing
crossroad
danger
direction
electric
electrical
equipment
flash
illuminated
industry
infrastructure
iron
journey
lamp
light
line
long
metal
public
rail
railing
railroad
railway
red
road
roadway
semaphore
sign
signal
sleeper
station
steel
stop
stoplight
track
traffic
train
transport
transportation
travel
urban
wait
warning
way