cable
control
direction
electric
electricity
energy
equipment
hazard
industrial
industry
intersection
lamp
light
line
lines
logistics
metal
object
old
perspective
pole
post
power
rail
railroad
railway
regulate
regulation
road
safety
semaphore
sign
signal
station
stop
supply
technology
telephone
tower
track
traffic
train
transmission
transport
urban
voltage
waiting
warning
wire