Daughter Scoosh needs to get her survey listing a bit tighter. No trams in Newcastle (T&W Metro) or London (DLR) - absolutely no possibility that you'd be riding anywhere near rails on DLR, and if on Metro you'd probably be trespassing and riding on ballast.
Interesting that they have focussed on trams , as there are probably as many crashes on level crossings, and other street ironwork (manhole frames protruding more then the 3mm limit above the abutting road surface - yes - go check!), although obviously the profiles and plan areas are different.
I suggest that the friction issue cannot be considered in isolation. I've identified 5 ways in which interactions with grooved rail embedded in a road surface can cause loss of control for any wheeled vehicle, some are also speed dependent, as I tested (slightly unintentionally) on a level crossing the other month. Travelling more slowly on the regular track my front wheel was deflected and dropped into the groove. I went back and crossed at a more normal speed - no problems.
I gather that there are some locations in Edinburgh where the crossing angle might suggest a rash of falls, but the way that the cyclists cross the rails avoids this (fast*, and without turning or braking) and the road surface surrounding the rails is smooth and high friction
* perhaps counter intuitive but with the greater rotational inertia in the wheel acting against forces trying to turn it or slide sideways (in some circumstances*) make a fast and straight crossing of rails inherently safer.
The potential for a massive variation in the available contact patch (1 point, 2 point, being unloaded by profile of surface, in contact with/without high friction surface under part of the contact patch (eg rail head = 50mm contact patch = 110-120mm x 10-20mm - 'ellipse')
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