Hi Richard, yes the stone viaduct in the distance on the left is also on a curve which continues beyond the end of that viaduct, all in all it probably turns through 120 degrees before turning back again the other way. In between the two bridges is Saltash Station, the image below shows a train leaving the bridge in the opposite direction and entering Saltash station which itself is on the curve. There's a 15mph speed limit across the bridge and not too much faster after that. My cousin was a Plymouth based driver, at one time they worked trains through to London, but then it was changed and they didn't work beyond Taunton. He wasn't best pleased, much of the high speed running occurs east of Taunton on towards London.I used to enjoy watching the long sleeper trains crawling across Brunel's bridge on their way into Cornwall. It's a tight corner on the other side to approach the next bridge, which I can see on the left of your picture in the background. Much squealing of wheels, as I recall.
Aha.View attachment 242298
Waiting to exchange the token
The signalman at Bishop's Bridge Signal Box on the South Devon Railway is waiting to collect a token from the train driver and pass on another for the next section of track. The token locks signals and points to the next signal box along the single track line hence preventing another train from entering the section coming in the opposite direction so preventing a head on crash.
Bart, I've just had to look this subject up, so I'm probably saying more about my age than you are about yours Never mind, I guess I've been benefiting from something I never knew about, at least in it's electronic incarnation, although the system on the railway is both mechanical and electrical in the sense that good old copper telehone connections are required between signal boxes..Aha.
That's where the idea of the Token ring came from
(guess I'm giving away my age here )