How do buses (like SF Muni) that run on overhead electrical wires stay on the wire when two wires intersect?

Question

How do buses (like SF Muni) that run on overhead electrical wires stay on the wire when two wires intersect?

Answer 1

"Trams draw their power from a single overhead wire at about 500 to 750 V above earth, while trolleybuses draw their power from two overhead wires (powered at similar voltage). Because of that, at least one of the trolleybus wires must be insulated from tram wires. This is usually solved in the following way: the trolleybus wires run continuously through the crossing. The tram conductors are slung a few centimetres lower than the trolleybus wires. Close to the junction on each side, the wire merges into a solid bar which is angled to run parallel to the trolleybus wires for about half a metre. Another bar similarly angled at its ends is hung between the trolleybus wires. This is electrically connected above to the tram wire's catenary cable. The tram's pantograph bridges the gap between the different conductors, providing it with a continuous pickup.

Where the tram wire crosses, the trolleybus wires are protected by an inverted trough of insulating material extending 20 or 30 mm below the level of the trolleybus wires. The tram pantograph or bow collector raises the conductor wire a little as it passes under. These troughs are presumably to limit how far it can do that and to provide a backstop to prevent the tram pantograph or bow collector ever touching the trolleybus wires.

Several cities use the above system. Until 1946 there was a level crossing in Stockholm, Sweden between the railway south of Stockholm Central Station and a tramway line. The tramway operated on 600-700 V DC and the railway operated on 15 kV AC. Some crossings between tramway/light rail and railways are still alive in Germany. In Zürich, Switzerland the VBZ trolleybus line 32 has a level crossing with the 1200V DC railway to mount Uetliberg; at many places in the town trolleybus lines cross the tramway. In the Swiss village Suhr the tramway WSB operating at 1200V DC crosses the SBB line on 15 kV AC. In some cities, trolleybuses and trams have shared the same positive (feed) wire. In such cases a normal trolleybus frog can be used.

Another system that has been used is to coincide section breaks with the crossing point so that the crossing is electrically dead."

I got this except from the wikipedia website.  There's more about the historical aspect of it and how it differs from other foreign countries.

Answer 2

The wires are all part of the same grid.  The bus simply rides the bottom of whatever wire or junction it's crossing.  A short break in the contact is covered by onboard batteries.