The four shortlisted engineering conglomerates bidding to build the trains for London’s �16 billion Crossrail ‘super tube’ were issued with the tender documents at the company’s Canary Wharf HQ today (Tues).

The documents have to be returned by the summer and final contract is awarded in 2014, with trains starting to roll off the production line in 2017 in time for Crossrail opening the following year.

A fleet of 60 trains is needed when the line connecting east London and Essex to Heathrow comes into service in 2018.

The documents set out Crossrail’s requirements which include the air-conditioned trains long enough to carry up to 1,500 passengers—double what a London Underground train carries—and have connecting ‘walk through’ carriages.

Crossrail will run up to 24 trains during peak hours from Whitechapel through the City and West End to Paddington, with only four stops between, some continuing on to Heathrow or Maidenhead.

Eastward from Whitechapel, the line splits with one branch to Stratford and Shenfield in Essex, the other to Canary Wharf and Abbey Wood in south-east London.

The four vying for the big contract are Bombardier Transportation (UK), Construcciones y Auxiliar de Ferrocarriles, Hitachi Rail Europe and Siemens.