10-28-2014, 12:45 PM
I suspect that there would be relatively technical limitations that us lay-people wouldn't quite get.
Potential problems I can imagine, from fitting 3 tracks under a 2-track bridge:
*) Less leeway for sway of the trains. This might limit kinds of cars allowed to pass at the bridge.
*) Rails may have a slight bend towards each other, to run under the bridge, limiting speed.
*) No buffer under bridge for derailment. Any derailment would likely hit the pier, and cause substantial damage.
These are entirely amateur guesses.
Potential problems I can imagine, from fitting 3 tracks under a 2-track bridge:
*) Less leeway for sway of the trains. This might limit kinds of cars allowed to pass at the bridge.
*) Rails may have a slight bend towards each other, to run under the bridge, limiting speed.
*) No buffer under bridge for derailment. Any derailment would likely hit the pier, and cause substantial damage.
These are entirely amateur guesses.