[ih] Speaking of layering and gateways

[John Levine]

Back in the 19th century there were a lot of railroads built in a lot
of incompatible ways. The most obvious incompatibility was track gauge
but there were others including the couplers between the cars and the
ways they did (or sometimes did not) ensure that there was only one
train at a time on each piece of track.

These days most of the world has converged on standard gauge but there
are still places like Spain and Russia that use broader gauges, and
mountain railways and trams that use narrower. When a passenger or
freight train crosses a border there's a variety of approaches, some
of which may seems kind of familiar.

The conceptually simplest approach is a gateway, at the border
everyone gets off one train and gets on another.  The Canfranc
station in the Pyrenees at the France-Spain border was famous
for this.

https://en.wikipedia.org/wiki/Canfranc_International_railway_station

Another approach is layering. At the border, equipment lifts the car
bodies off the bogies of the old gauge and puts them onto bogies of
the new gauge. This is better since passengers don't have to get out
(often from sleepers in the middle of the night) and goods don't have
to be unloaded. This technique was patented in 1876.

Here's the Prague-Moscow train changing gauge in Brest, Belarus.

https://youtu.be/2nI467sc-Eo?si=w783HVwUGXAmQD7_

Yet another approach is parallel operation, dual or triple gauge, with
three or more rails allowing trains of different gauge to run on the
same route. In Japan the Shinkansen are standard gauge but older
railways are mostly 1067mm so there's a fair amount of dual gauge in
and out of cities.

This is a very old solution. The Niagara Falls bridge in 1855 had four
rails for three different gauges, although now it's down to two.

Here's a video of a dual gauge Shinkansen route:

https://youtu.be/0d0XAaqEZ0s?si=ZYo27gNoAAXibtVq

Another approach is switching on the fly. Some trains have variable
bogies that can change gauge as the train is moving, which is pretty
cool.

Here is a Swiss train doing that:

https://youtu.be/H0gj2LWe-SI?si=7zpZFc-jQPTIv8TX

And a tutorial in Spanish:

https://youtu.be/y8N7Ikw87tM?si=bCwrx5ph3SpgrevM

The last approach is a flag day. One of the reasons the south lost the
US Civil War was that they had a fragmented rail network, which
continued to inhibit recovery and development after the war. So over
two days, May 31-Jun 1, 1886, southern railroads regauged 11,500 miles
of track to the Pennsylvania's gauge (1/2" wider than standard but
close enough) and changed the bogies on the rolling stock.

Here's a video about it:

https://youtu.be/4v81Gwu6BTE?si=Yi9JDSU0onABpWju

R's,
John