Overhead: Streetcar pantograph

The overhead is fascinating. The streetcar travels on the same roads that accommodate electric trolley  buses. The streetcar uses a pantograph (shown) while the trolley buses use poles with "shoes" that fit over the lower part of the wire. 

How to keep the two systems apart without causing short circuits? The accompanying photo shows a streetcar under wire on Fairview Avenue. Note the double wires parallel to the single streetcar wire. These are for the Route 70 electric trolley bus.