http://disused-stations.org.uk/t/thorp_arch/index.shtml
Due to the large number of workers at the site a six and half mile circular railway was built round the complex. Trains travelled one way (clockwise) and they dropped off or picked up staff from four separate stations on the line. This helped staff the long walk to their working areas. The line was fitted with colour-light automatic signals, so several trains could run round at once.
It must have looked like a giant railway train set.
Glencairn