A train bridge is a type of bridge that is specifically designed to support the weight of a train. It is also known as a TRESTLE bridge, which is a bridge composed of a number of short spans supported by closely spaced frames. The term 'TRESTLE' comes from the Latin word transtrum, meaning 'a beam or girder supported at both ends.' TRESTLE bridges are often used in areas where there is not enough space for a traditional bridge, and they are also used to cross rivers and other bodies of water.