If you fly over England at the time of the morning peak you will see busy main roads into cities and towns with cars often bumper to bumper. You will also see near empty railway lines, with a couple of miles gap between trains. Hundreds of cars an hour pour into our urban areas, whilst just 27 trains an hour make it over our main line tracks.
So why do we need such large gaps between trains? After all, trains on the main lines are all going in the same direction on any track, so there is no danger of a head to head crash. They all have drivers and brakes, so they should all be capable of closing the gaps without endangering passengers.
The main reason is Network Rail still uses an old fashioned signalling system based on fixed block. This means that signals keep a second train out of a section of track all the time the first train remains in it. Because there has been a history of train drivers passing red signals there are various automatic warnings and braking devices to try to stop trains ending up close to each other.
There are now new systems based on radio links, computers and satellite positioning that enables an individual train to know where it is and how far it is away from the train in front. As these systems become more commonly adopted it should be possible to run 30 or even 33 trains on the same piece of track, providing a 10-20% increase in capacity.
All of this is still far from ambitious. It should be possible with new computer aids to run up to 40 trains an hour safely over the same track. It is clearly easier to do that if all the trains have good braking systems and similar speeds. As soon as you introduce slower trains into the system you need by pass track and better controls.
These new systems offer us the best way to a safer railway with more capacity.