For the driver of a commuter train, the journey north from Blackfriars station, in the City of London, is nerve-racking. As the train leaves the Blackfriars platforms, it starts to fall one metre in height for every 29 metres it moves forward, the steepest slope on the UK’s railways. To make matters worse, in future the driver may have to accelerate fast down this slope within sight of a train still standing at the platforms of the next station, City Thameslink.

The City incline and another, similar slope at the northern end of the Thameslink cross-London route’s central, tunnelled section are a significant reason why Network Rail, the owner of the UK’s rail infrastructure, is considering making the route one of the world’s first heavy-rail services to use automatic train control. The technology, which is common on metros, retains a driver in a cab at the front of the train but hands over normal, minute-by-minute control to a computer. As part of a huge, £5.5bn ($8.9bn) upgrade of the route, Network Rail needs to make the central Thameslink section capable of handling 24 trains an hour by 2014. Humans driving a train down the City incline would never dare to accelerate at the necessary speed to run such a service. But computers would.