No matter how fast a high-speed train travels, it still has to slow down to 0 mph to pick up additional passengers. That problem has been solved by a designer who dreamed up a way for high-speed local trams to catch up to those speedster trains, picking up and dropping off passengers without requiring the express train to stop.There's video. Imagine track-level rendezvous, docking, opening the airlocks, albeit in the presence of atmospheric pressure and gravitational clues that the target and chase vehicles are in motion.
If you think about it, this is a problem that needed to be solved long ago. You've probably noticed that trains (and buses, too) waste a lot of time slowing down, pulling into stations, waiting to pick up and drop off passengers, and then speeding back up again. But with this idea, high-speed trains might be able to keep on rolling indefinitely, while those feeder "trams" do all the slowing down and speeding up.Half the problem was solved long ago.
‘Through Carriage to London’ announced the proud notice at Stratford Old Town as the 7.45am train for Blisworth prepared to leave from the ‘Up’ platform sometime in the 1930s. Would be commuters were directed by station staff to a smartly maintained LNER ex-Great Central slip coach attached to the back of the train. It contrasted greatly with the two ancient now LMS owned coaches which formed the rest of the train. As the signal pulled off the train set off at a leisurely pace towards Byfield, stopping en route not only to pick up the occasional passenger but also milk churns bound for London via the Great Central route. At Byfield the slip coach would be met by a LNER loco probably an ex GCR N5 tank and whisked off around the curve to Woodford, along with the milk churns, where it would be quickly attached to the Mansfield-Marylebone express. Passengers in the slip coach would arrive at Marylebone at 10.48am after a 3hr 3mins journey. Not exactly express standard.It's not the safest practice, and in the United States it is unlawful to move occupied passenger equipment without a locomotive attached. In Britain, slipping might have originated by accident, but it became a way for a railroad to deliver passengers to intermediate stops more quickly.
The return journey to Stratford would be more exciting and much quicker too by means of the crack 6.20pm Bradford express. The slip coach having been carefully checked over under cover at Marylebone, would be attached to the main train, with a further slip coach behind it which was destined for Brackley. This was to be slipped at Finmere and worked forward to Brackley tender first by a Woodford loco, often a B7 ‘Black Pig’. There was much competition for the perceived potential first class custom in ‘Lark Rise to Candleford’ country and the Finmere slip coach was in direct competition with GWR slips made at Bicester. Both slip coaches were protected at the rear by both white and red lamps and were manned by Marylebone based guards, while the main train guard would be a Leicester man.
If a carriage could be left behind by accident, and convey passengers safely to a station at which the train did not stop, why could it not be done deliberately and thus save delay ? In a short time the slip-hook coupling was evolved, and the slip-coach, as we know it to-day became a regular feature of railway operation.With fully-automatic couplers that make or unmake brake and communication line connections concurrently with the addition or deletion of cars, wouldn't the simpler solution be to do adds and drops on the fly? On the other hand, particularly with rapid-transit equipment, a drop or add can be made in a stop of about a minute.
The slip portion of a train is not limited to one coach only ; so long as the coach with the slipping apparatus is placed next the "fixed" part of the train, the slip portion may be made up to any required length within certain limits.