What if you could run more trains on a railway by coupling different trains while they are running? That is the aim of Israeli startup DirecTrainSystems (DTS), building on know-how of refuelling airplanes mid-air. This also sounds difficult, but has been in practice for many decades. The company will give a workshop on RailTech Europe on 21 June about the concept of coupling trains.
The idea in itself is quite simple: by physically connecting running trains, more trains can run on the same track. Once coupled, the usual minimal distance for braking no longer applies. “The number of passenger train services on a line can be increased, as will the capacity for freight”, says DTS CEO Alberto Mandler. In an analysis carried out with Delft University of Technology in the Netherlands, an increase of capacity of up to 40 percent could be achieved based on simulations. This would require changes to just 1 percent of the existing rail infrastructure.
Platooning intercity and commuter trains
Ishay Erel, business development manager of DTS explains: “Imagine point A in the suburbs of a city. A direct train from the suburbs (A) to the city center (C) does not stop at any stations in between. Due to capacity constraints, an additional train from intermediate station B to the city centre is not always possible. With dynamic coupling technology, a train leaving station B could physically connect to the direct intercity on the way, and together run into the city centre. This connected train, or platoon, requires less space on the tracks.”
Mandler and CTO Moti Topf are both engineers, and have a background in aerospace design. This expertise, they say, can also be translated to the rail sector. Moti Topf: “Refuelling in the air is arguably even more difficult than coupling moving trains, yet coupling trains has not yet been developed.”
Coupling trains on the move is not the issue. Nor is uncoupling them on the move (see slip coaches: https://en.wikipedia.org/wiki/Slip_coach). The challenge is to get them into a position where they can couple and then uncouple.
Let’s postulate a faintly plausible case (assume coupling compatibility).
We’ve sent a 12-car train from Euston on the slow lines towards Watford Junction bound for Northampton first stop Milton Keynes, Once it passes the junction just south of Wembley Central, the following 8-car train from the West London Line, fast to Milton Keynes Central can be signalled to join the main line. This train will be, say 90 sec behind and will have to accelerate to catch up with the one in front if they are to couple, or the front one will have to slow down. This will create a bottleneck affecting the ability the headway to any following train. They’ve now coupled into a 20 car train, and can proceed along the line. Somewhere on the approach to Milton Keynes, probably at around Bletchley, they uncouple. The second train has to slow down so that the first train can clear the junctions approaching MK, so the points can switch to allow the terminating platform to be cleared for the terminating platform; another bottleneck.
I think this illustrates that it’s the splitting and joining that will determine determine capacity not the plain line headway.
There have been experiments in running two freight trains coupled together to save paths, but they couple and uncouple in when stationary!
I did see a proposal for branch line trains to run on tracks adjacent to though line trains with their speed synchronised allowing people to change from main line to branch line and vice versa whilst the trains were moving. Even more bonkers!
I’m not happy with this concept and I’m not sure they’ve thought this through. “Once the technology is proven” means they haven’t done it yet, and doesn’t fill me with a great deal of confidence. Communication between the trains has be absolutely reliable: there is little or no room for error. The coupling system needs to be absolutely reliable and if some form of multiple-unit configuration exists that requires physical and electrical connection it has to be of the most robust design. Should the coupling fail, what mitigating procedures need to be put into place? Have they thought about this? Uncoupling seems relatively straightforward though, but there needs to be an absolutely reliable method of overriding the automatic braking systems over the detaching sequence and then flick back into action when the process is complete. Also, I believe there were a few historical incidents when slipped coaches have caught up with the leading train due to defects or the leading train braking suddenly. We, as they say, shall see,,,
The ‘coupling’ need not be physical in the future. The developments also include digital coupling of synchronised units for a convoy under the lead control.