The UK railway network is at breaking point. Each year there are more people using it; last year there were 1.6 bn passenger journeys.

There has to be a drastic increase in capacity. This usually costs an enormous amount of money, so an alternative approach has been drawn up.

It's called the digital railway.

Mega Builds is a video series from BBC Future looking at giants of engineering from around the globe.

Video script: Ed Barrett, from the Department of Science and Technology Studies, University College London