The construction of the Crossrail project began at North Dock in Canary Wharf in May 2009. At the height of construction it was the biggest railway construction project in Europe and is one of the largest single infrastructure investments undertaken in the UK. It consists of 21 km of new twin-bore tunnels under central London and 10 new world-class stations across one of the largest cities in the world. Crossrail Project: Infrastructure Design and Construction Volume 6 contains a collection of 22 papers submitted to the 2021 Crossrail's Technical Papers Competition. Contributions have come from members of the Crossrail organisation, its consultants as well as contractors involved in design and construction across the Crossrail project. The papers cover a multitude of disciplines including tunnelling, geotechnical engineering, rail signalling and control, rail systems & integration, rail telecommunications, and electrical engineering. As part of the enduring legacy of the Crossrail project, it is incumbent upon the organisation to share its experiences and best practices with the rest of the industry, to showcase the skills of the personnel involved and the successful delivery of each phase of works. Crossrail Project: Infrastructure Design and Construction Volume 6 offers more high-quality papers on the best practice in design and construction for large-scale underground projects.