Conduit slot trolleys

There's a large collection of DC trolley photos here. At the end the fleet was PCC cars, ex-cable cars were probably gone by the 1920s.

This video shows the Georgetown Plow Pit.

There were two conduit systems in the US that I know of, Washington, DC and Manhattan.  Both were built as conduit systems, not converted from cable cars. There are drawings around, but I do not have any. They are not really third rail systems.  In the conduit were both + and - polarities for the DC traction circuits.  Neither were grounded. The rails were not used as a power conductor.   This was done to try to reduce ground faults.  I believe National Capital Trolley Museum has a section of conduit track they recovered from the street.  It was quite massive to try to keep everything in the proper location. 

Here are some shots I took of the Georgetown pit back in the 1950s.  Lew

National Capital Trolley Museum has a conduit section removed. O, P, and other streets in Georgetown, where the track had still been in place, has been restored and can still be seen. The track in front of Glen Echo Park has also been relaid but that is not a conduit section. 

Sorry for such a terrible photo....this is an old one with a very old junky digital camera. Was at NCTM last week with my new equipment but didn't take an updated photo of it. 

ONE THING ABOUT THESE SLOTS IS THAT THEY COLLECTED DEBRIS.THE GREEN LINE BOOK FROM NEW JERSEY INTERNATIONAL GOES INTO THIS IN DETAIL.

The conduit became popular because stray currents were destroying gas lines through electrolysis.  Beneath the slot there were two conducting bars, on either side and the "plow" contained two sliding "buttons" that were spring loaded, keeping them against these bus bars. The "plow" moved from side to side. The "slot" was not always in the center. On 42nd street there were two slots in places. In New York sometimes one slot was for cable cars, the other for electric vehicles. In other areas there were two slots but different companies sharing rails.

London UK also had conduit operation.  This website has articles on laying new track 1951 and  the ploughs, plus conduit oddities. Probably some of the best photos I have seen.

The Smithsonian has or maybe had before the transit hall renovation (ten years ago or so)a section of DC conduit displayed under their DC trolley car. I grew up in the area and haven't been back since the renovation.

Good point - didn't think of it. Sorry I don't have a clear picture but you can make it out in these photos from May.  

Interesting the old display was raised and had a section of exposed under street conduit.