caution
complexity
construction
control
controller
cross
crossing
crossroad
curve
danger
direction
electrical
equipment
forward
illuminated
indicator
infrastructure
intersection
journey
junction
lamp
light
line
metal
metro
pebble
public
rail
railroad
railway
roadway
safety
signal
speed
station
steel
stop
terminal
track
traffic
train
transport
transportation
urban
vanishing
wait
warning
way
wreck