The Eiffage, Kier, Ferrovial Construction and BAM Nuttall JV is responsible civils works between the North Chilterns and South Warwickshire, one of the longest sections of HS2.
She will take up the position in December, where there will be a transition period with incumbent managing director, Mark Pengelly, who will retire from his role at the end of the year.
Cox brings to the role more than 30 years of experience in the rail and civil infrastructure sectors both in the UK and abroad, including her most recent position as project director for the Tideway West tunnel in London.
Prior to her work on Tideway, she was managing director for Hochtief UK Construction and project director for several significant rail projects in Australia.
The JV is also responsible for constructing 15 viaducts, over 5km of green tunnels and 81 bridges and is committed to supporting local communities, with over 50 community investment projects carried out to date in areas close to the works.