Prolonging the life of existing steel trusses all over the world is a incoming necessity for all managing authorities wherever these structures have reached a particular state of use. The unsatisfactory behavior of these structures under the current type and increasing number of loads make clearer that innovative solutions are needed. For this purpose, the realization of different techniques are presented, in order to retrofit the actual load onto a structure conceived with historical codes, characterized by lower design live loads. The possibilities of retrofitting bridges with different solution studied in a recent research program are presented and compared in this study.