The former longest twin span bridge in the world spans 655 meters long over Delaware river. You're not seeing double (unless you're seeing four bridges) Delaware Memorial Bridge is actually two separate suspension bridges. The first bridge was completed in august 1951 at a total cost of 44 million US dollars. It is dedicated to the dead of the Second World War. The bridge is designed by a firm, known today as HNTB with consulting help from the master builder Othmar Ammann. The bridge proved to be very popular and in 1960 over 15 million cars per year crossed it. This called for a second bridge, since the original one couldn't be widened to accommodate the ever growing traffic volume. Construction of the second bridge, almost identical one, began in 1964 and was completed four years later. The second bridge is dedicated to the dead of the Korean and Vietnam War. The second span cost 77 million dollars to build, over 1,5-times the cost of the first one. Both bridges have a center span of 655 meters and 53 meters of clearance below. The decks have four lanes both. The first (western) bridge carries New Jersey-bound traffic and the second (northern) bridge carries Delaware-bound traffic. Both bridges can be converted to two-way traffic, should either one be closed. The four 127 meter tall steel towers support the four 20 inch (~50 cm) thick cables that consist of 8,284 individual wires each.