There was an interesting in "Rail" this week about the Isle of White railway, and the problems replacing stock
It's the Isle of
Wight, and the D Trains are too tall for the loading gauge - as much if not more of an issue for some of the bridges than the tunnel itself.
Pre-conversion D Stock, without the increase in height or the diesel engines, would be more practical but may still need work to fit - vehicle length would also be an issue at Ryde Esplanade with it's sharply curved platform.
Lowering the trackbed is probably not that difficult or costly, however the fact is it was raised because of regular flooding - so surely lowering Ryde tunnel would increase the flood problem?
At most the pumps used to cope with water ingress at high tides might need to work a bit harder - it wasn't an issue when 503s were proposed in the 80s so it shouldn't be now.
Most if not all recent floods have been caused by Monktonmead Brook bursting it's banks - that would happen whatever the height of the track through the tunnel.
I also understand that the track does continue to fall once inside the tunnel!
Not really, no - it's cut and cover.