barrier
business
caution
cross
crossing
danger
direction
electric
energy
fast
flash
industry
iron
journey
junction
light
line
metal
perspective
power
public
rail
railroad
railway
red
road
rural
safe
safety
security
semaphore
sign
signal
sky
speed
station
steel
stop
symbol
track
traffic
train
transport
transportation
travel
tree
warning
way
white