The junction covers 30 acres, serves 18 routes and includes 4 km (2.5 miles) of slip roads. There are five levels, and it flies over two railway lines, three canals and two rivers. It took nearly four years to build it, against an estimated three years. It cost £8 million, which is a deceptively small amount. It can only be understood by realising the extent of monetary inflation during the past half century.