Lots of systems, San Francisco included, share wires rail to bus. As long as the bus is 600 v dc, which it usually is, they can share power. They only share the hot wire.

The one thing that isn't done is for a pantograph-equipped car to share overhead with a trolley-bus line. This is one reason why the San Francisco "F" line vintage electric streetcars use the traditional trolley poles rather than modern current collectors. Where a route only has rail cars, the overhead can be set up for both poles and pantographs.

At one time Chicago Surface lines had a fleet of trolley buses equipped with a small set of railroad wheels on the rear. This allowed the buses to be operated on single wire streetcar lines with one pole raised and the wheels providing the return. I know this system was used to move buses from remote lines to their barn. I do not know if they were used in service.
GME

There are pictures of Minneapolis buses with rail ground return too, in Olsen's "Electric Railways of Minnesota".

Hi,

Generally speaking, i think most transit systems that operate trolley bus and light rail systems would operate on the same voltage. I can really only speak for the one I work for in San Francisco. On Market St. the streetcar shares the hot wire with the trolley coaches. And in places there are four plus sets of wires (2 sets inbound and 2 sets out bound plus related crossing + crossovers).

The trolley coaches, the ground is the "other" wire.

Speaking of Gauntlet track, Lisbon, as best I know still operated Gauntlet track either on route 12 or 14. It as great being on these single truck cars, operating at some speeds up and down these very narrow streets and then find the car on gauntlet track, going quickly around a bend in the street. I'm not sure what sort of signal system they had, but the operators certainly stepped the cars along.

Cheers--Karl J.

I just remembered how San Diego Trolley used gantlet track on a couple of bridges on the La Mesa/El Cajon line until they could add second spans to the crossings (I think both were over freeways, and were left over from the San Diego & Arizona Eastern freight service days.)

When Tri-Met built the Red Line to Portland International Airport, a small section of gantlet track was used where the Red Line diverged from the Blue Line at the Gateway Transit Center. The Red Line does a 180 degree turn leaving south from the Gateway station, turning north to run alongside I-205 before entering the median of the freeway towards the airport. The location of Gateway on the east side of I-205 where it meets I-84 meant there was limited space to construct the elevated 180-degree turn, so using a gantlet track was logical. The newer Green Line also diverges at Gateway, running south in the median and western perimeter of I-205 towards Clackamas Town Center. The Green and Red Line segments along I-205 were built in the right-of-way that was reserved for the planned busway (BRT) when I-205 was constructed.