Your questions answered: Crossrail

With a marathon’s worth of tunnels under one of the most densely populated and complex cities in Europe, the sheer scale of London’s new railway line is overwhelmingly impressive.

The £15bn Crossrail project needs to accommodate 200 million passengers a year across a total of 100km of track with 40 stations (including 10 new ones).

Work began back in 2008 and most of the tunnelling is now complete — but services won’t start running until 2018 so there’s still plenty to do.

For the latest in our series of reader Q&As, members of the engineering team behind Crossrail have answered your questions on the difficulties and innovation of the project.

Which were the trickiest parts of London to tunnel underneath and why?

Mike Black, Crossrail head of geotechnics, and Mike King, Crossrail head of underground construction:

Crossrail is among the most ambitious infrastructure projects undertaken in the UK and will dramatically change how people travel across London.