This paper describes the results of the NAKI II project of the "Methods for Achieving Sustainability of Industrial Herirage Steel Bridges" which has been carried out over the last 5 years. It deals with the diagnostics results present the overview of the load tests done and assessment results, including the coating application. The strengtening methods are presented, with the focus on the SMA materials. It is shown, that we have still many hidden reserves in the load capacity of heritage bridges, and if proper methods are chosen, the durability can be much longer, then predicted 100 years.