Jacobs Engineering and Atkins have received design contracts from the UK's Network Rail for the 118km-long Crossrail network in west London.
US-based Jacobs Engineering is expected to handle construction work on a new flyover near Heathrow Airport.
Atkins will undertake the design element of the project to redevelop Acton freight yard, according to news.careerstructure.com.
The project is also expected to include a dive that will allow more freight trains to leave and enter the yard without affecting passenger trains.
The construction of the Crossrail network, serving London and the south-east, is scheduled to be completed in 2017.