In this paper the most relevant and an important aspect of the motorway crossings is presented. The composite bridges are, in comparison with steel bridges and concrete bridges, the most proper solution for motorway crossings because they are efficient, the erection time is shorter and the “in situ” operations can be minimized. The attention is focused on general design criteria of these crossings. Fabrication and erection methods have a big influence on the detailed design of the steel structure. The supporting steel members must be designed so that they do not interfere with the placing of concrete slab.