I have followed both U.S. and European railroads for many
years and may be able to provide a little information.

First, the contemporary UIC coupling system is best
described as buffer and screw-link, rather than buffer and
chain. The screw-link is adjustable to remove slack.


Back in the 1970s, the UIC tried to introduce an automatic
coupler that would have been implemented Europe-wide in
two versions. The first version would have made the coupling
and also connected air and electrical connections for passenger
cars. The second (simplified) version was intended for freight
cars and would only have connected the air line.

The two couplers were compatible, meaning that you could couple
freight cars behind a passenger car, once you no longer needed
electrical power. All mainline locomotives were to receive the
more complex passenger coupler, but, could, of course, couple to
all freight cars.


Considerable research went into this project. (I have a book on
the subject, in German.) But, ultimately it failed due to cost
and political considerations. The change-over would have required
almost all rolling stock to have been converted in a period of
about two weeks. The eastern European countries simply could not
afford the costs, and if only western European countries had
converted, this would have resulted in chaos in train makeup.

Even before the fall of the Iron Curtain, there was lots of cross-
border traffic between western and eastern European countries.


One reason that the conversion would have been so expensive is that
-- particularly in eastern Europe -- there were many older freight
cars that were simply not strong enough to have both the draft and
buff forces through a central coupler.

The Eurocoupler was implemented in a few test locations where rolling
stock operated only on a given route with the same motive power. One
example was a shuttle train carrying automobiles through a long Alpine
tunnel. The locomotive switched ends using the automated couplers.
(This operation has since been converted to push-pull with a cab
control car at one end, eliminating the need to uncouple.)


As indicated in the Wikipedia article cited in another post, many
dedicated European passenger trains (high-speed trains such as the
German ICE) do use central Scharfenberg couplers. On these lines
and at major stations, there are a few electric locomotives equipped
with a hinged Scharfenberg coupling, which can be swung into position
if a disabled train with the Schaku needs to be towed.

A lot of the need for coupling and uncoupling of passenger cars in
Europe has gone away. Kurswagen -- through cars that go from one
long-distance passenger train to another -- are now rare. Most
short-haul passenger trains are run with either multiple-unit
(EMU or DMU) equipment or are push-pull with a cab control car at
one end. That eliminates the need for the engine to change ends.

On dedicated unit freight trains, such as intermodal trains, there
are both articulated multi-platform cars and dawbar-connected cars,
again reducing the number of coupler locations.


Some unit ore trains in Scandinavia do use knuckle couplers. The
engines have retractable buffers and can still connect with standard
UIC coupler equipped cars.

For now, there is little likelyhood that the UIC coupler will go
away alltogether.

-- Ernest