Railway convoys

The letter from David CooperSmith and the opinion column on Digital Railway by Philip Haigh (both RAIL 837) have an interesting connection.

One important consideration in comparing road ‘platooning’ with the possibilities on rail revolve around the essential difference of road not being signalled, in the sense that vehicles can follow each other as closely as they like.

But while road vehicles may be able to travel much more closely together using WiFi, the fact remains (as now): if the lead vehicle comes to a catastrophic stop, the closely following vehicles will also immediately run into the back of each other, multiplying the effect of any initial collision.

We have seen this happen under conventional operation - neither road nor rail can stop instantaneously.

With rail signalling however, whether by conventional or digital control, there will always have to be a gap sufficient to permit following trains to stop in a controlled manner clear of any sudden obstruction.

This does not change the issues with regard to trains approaching on other lines, and nothing is likely to radically improve that risk. Moving block signalling can obviously permit trains to run closer than under most conventional systems, but it is certainly not the answer to all capacity issues as Philip’s article makes clear. John H Brook, Chapel-en-le-Frith