Hi
In Bordeaux (a city south west of France, there are tramway rails with a center rail (only in the city center to avoid hugly catenaries) which is only active (with 600 V Voltage) only when the tram is there (puling- up the piece of metal to close the contact.
this is to avoid any danger to pedestrians walking near on a rainy day.
Here you see the transition between a catenary section and a centre-rail section.


On the London Underground, there are some lines with a center rail and a side rail to provide power.

So center rails or studs are not so rare

Jean

Interesting and that on/off switch better work every time

Sydney's L2 and L3 lines also use this system: https://en.wikipedia.org/wiki/Alstom_APS

Hi Kimbal
Thanks for your input
Here is a picture of the tramways in Tours (France)

There seems to be a center rail to bring power BUT, there are technical possibilities NOT to have any power lines (above or below)

The trams are Alstom Citadis ones (very low floor and optional overhead, ground or battery power supply). So in one of the variants you may have a strech of line without any power at all.

In France we are a bit maniacs not to spoil the city centers with overhead wires, noise or huge advert signs even though today, sadly we have strikes about the retirement age which in my opinion is stupid (I worked until 71 and I finished my career in the UK to avoid having my pension suspended). Maybe it is an excuse for unions to show their power.

Cheers
Jean