I have laid two more lines of track on each traverser. This gives eight lanes in total, which should be enough to be getting on with. (I can always add more later, if I find I need extra space !)
The electrics are complete too. For one traverser I connected one wire to each rail, giving a total of eight wires on the traverser (see above).
For the other traverser I used just two wires, essentially a series connection.
The end results look quite different. I feel one looks like a piece by Rachmaninoff (complex, with full orchestration [if you are pressed for time just listen to 6’50” to 8’05”]) and the other is more like a piece by Erik Satie (minimalist and meditative). Both work well. Who could choose which is best?