I have no idea if current maximum bridge weights are realistic or not.
However, Sheffield tram-train is too heavy for any available road bridge and it should be possible to build road+tram bridges that can carry that load, as it is also possible to construct bridges for much heavier trains.
I have just found an image of a bridge in sheffield tram network, although I don't know if that section is part of the tram-train line or not.
https://www.thetrams.co.uk/supertram/pictures/000619/image/original.jpg
Should we adjust the maximum weight of an existing bridge e.g. steel cantilever or concrete bridge or add a new one instead?
Or is this intended and tram-train should not be able to use and road bridges at all?
The Tram-Train can use the concrete road bridge, introduced in 1955, which has a 70t weight limit; the Tram-Trains weigh 66t each. I have just tested this, and the Tram-Trains will pass over the bridge.
The tram-train has a loaded weight of 72.16 tons.
Concrete bridges have a weight limit of 70t. A quite dangerous pitfall for any schedules.
Thank you for spotting that. I have now increased the maximum weight of these to 74t to avoid this problem.