• THE letter on automatic train operation (ATO) currently being built highlights yet more reasons why HS2 should be dropped (Can Siemens save Camden Town? March 15).

If anyone wants to see ATO in action, just head to the nearest Victoria line station. Tube trains on that line have used ATO since 1969. I’d often wondered how a Victoria line tube could be arriving as the one ahead had just left. The answer is ATO.

ATO is a train safety system. Development of ATO for mainline use is close. Hence the trains that Siemens is now building. Adding ATO to digital signalling and double deck (bilevel) trains makes a compelling case against HS2. Trains can run closer together – safely. More trains solves the government’s claim for increased capacity.

There are three types of digital signal systems: European Train Control System (ETCS) – known since 2002; European Rail Traffic Management (ERTM) – known since 2005; and, for the very near future, 4GLite; expect 4GLite to be well established by the mid-2020s.

As with double-deck trains, I’ve asked my MP why it’s taken so long for the government to look at them. So far just a bit in Philip Hammond’s 2016 autumn statement. He implied that digital signalling is “new”.

ROBERT COLES
Cubbington, Warwickshire