United Kingdom, May 2 -- The busy A46 Kenilworth Bypass was reopened to traffic last night 30-hours ahead of schedule after a major closure to allow Balfour Beatty VINCI engineers to slide a massive 14,500-tonne concrete box structure into position beneath the road for HS2.The huge box - which weighs around the same as two new Royal Navy destroyers - is the heaviest of its kind in Europe. It will allow high-speed trains between London and Birmingham to pass under the dual carriageway on their approach to the new Interchange station near the NEC.It is one of more than 200 major bridges and viaducts on the new railway, which is designed to improve journeys between London, the West Midlands and the north, while freeing up space on the existing...