United Kingdom, Dec. 30 -- The construction of one of the most complicated parts of the HS2 project took a step forward over the Christmas break, as Balfour Beatty VINCI completed two key viaduct spans over the existing railway near Water Orton in Warwickshire.The spans form a small part of the Delta junction - a huge triangular intersection being built to the east of Birmingham for the new high-speed railway.Like the nearby Spaghetti Junction, it is formed of a complex series of interconnected viaducts, taking the high-speed line over motorways, local roads, existing railways, rivers and floodplains. It is designed to carry HS2 services to and from Birmingham, as well as connecting to the mainline heading north and south.To maintain speeds...