some trolley buses had 2 poles live and return that is why you see 2 wires side by side ,,no tram track to earth out ,if tram track was there could use tram wire (bow) and track to earth out or neutral, London trams where more complicated overheads and skates ,(a middle groove running in centre of track and was very a hands on thing to do ,had to have a skate man to put them in place ,but could be thrown by a moving tram when removing them )as some places did not want wires put up