In message

..net, at 09:36:55 on Mon, 25 Feb 2013, Neil Williams
remarked:
SDO is normally used to allow one set of doors to be off the platform,
not an entire coach at each end.

SDO is presently used at Bletchley for 4 cars (a whole unit) off the end of
the 8 car platform on a number of trains. The platform is being extended,
but it has been used in that manner for well over 2 years.

Until they recently lengthened the platform, northbound HSTs stopping at
Loughborough had the rear three coaches locked out, and the front three
southbound. That's for decades.

They also used SUO (selective unit opening - I just made that up) on the
rear unit of some 4+4 (or maybe 5+5) Meridians between Nottingham and
Loughborough southbound in the morning each hour, opening up the rear
unit for the first time at Leicester.

Infamously, Meridians (like Voyagers) don't have a corridor connection
between the two units.
--
Roland Perry