Glen,
A bit of tecnical hairsplitting:
Second section following does not mean "Extra" section following. An Extra Train by definition is a train NOT covered by timetable but only given authority to run by right of train orders.
Back then your train was given priority by Right, Class and Direction. Class was conferred by Timetable.
Second Section following was a second train run on the same schedule as the first train, usually indicated by a 2-(Train Number). The Green lights on the first train was to warn crews waiting in the hole for the scheduled train to clear that a second train was following the first, running on the same rights. If the second train also had green lights, a third section of the same train would be following, and so on. The most sections ever recorded was seven on the Sunset Limited (IIRC). The last section would display no class lights as timetabled trains were not to display any class lights whatsoever.
Rick Steele