Three companies have been shortlisted for Highways England's largest single contract - a £2.3 billion project to build the longest road tunnel in Britain at the heart of the proposed Lower Thames Crossing. For more than 65 years the Dartford Crossing has stood as the only crossing between Kent and Essex - a critical link carrying vital food, goods and services between the manufacturing centres, ports, and distribution hubs of the South East, Midlands and North of England. It is designed for 135,000 vehicles a day, but now often sees 180,000 a day use it, leading to long delays which businesses across the country say act as a barrier to trade and jobs.