From Wikipedia: A Bailey bridge is a type of portable, pre-fabricated, truss bridge developed by the British during World War II. A Bailey bridge required no special tools or heavy equipment to construct. The wood and steel bridge elements were small and light enough to be carried in trucks and lifted into place by hand, without requiring the use of a crane. The bridges were strong enough to carry tanks. Bailey bridges continue to be extensively used in civil engineering construction projects and to provide temporary crossings for foot and vehicle traffic.