On Tehachapi Pass, the track is single line with passing loops (very long ones) as at Woodford. So the trains have to move from siding to siding to pass each other.
Even when they have a clear run they are not moving very quickly as the line has
steep grades, so they are either storming uphill or in dynamic braking mode creeping down. Would not want to lose control of a train as ther are also some tight curves.
For a tight curve at the bottom of a steep section, see the Caliente video. They really have to crawl around that and over the grade crossing.