With an ageing bridge stock and in order to limit economic and environmental costs, developing preventive maintenance, repair and strengthening strategies will help asset owners to make efficient decisions in a sustainable way. For steel and composite steel bridges, preventing fatigue failure is at stake. In this context, easy-to-apply preventive strengthening techniques should be developed to extend fatigue lifetime of steel bridges and delay resource-consuming major interventions such as traditional steel strengthening, rehabilitation, or decommissioning and new construction. This paper investigates the cost and environmental burdens associated with several strategies to extend steel bridges fatigue life-time. In particular, one details the needed information and the methodology for the implementation of an overall life-cycle analysis of an adhesively bonded CFRP solution compared with traditional techniques (use of steel plates). This is carried out considering economic, environmental and social benefits of the preventing policy and illustrating the developed methodologies with a case study corresponding to the strengthening of an existing steel bridge during its service life.