Some ageing bridges exposed to heavy traffic loads or abnormal loads may have critical details, either against extreme loads or in fatigue. Old bridges were designed with design codes and load models which are now exceeded by the authorized vehicle loads. Therefore, keeping the bridge safety and reliability at an acceptable level requires periodical reassessments of some structural parts, using updated traffic data, e.g. weigh-in-motion (WIM) data. For extreme loads and current ultimate limit states, extrapolated maximum axle, vehicle or total loads, depending on the considered effect and influence line length, are used to assess the maximum load effects which may be exceeded with a given probability. They are compared to the design loads affected of the partial safety factors. For fatigue limit state and lifetime assessment, the updated traffic loads, if available, or some estimation based on similar traffic flow, are used to calculate expected lifetime with the Miner's law and fatigue resistance (S-N) curves. These lifetimes are compared to the required ones, taking into account the elapsed bridge lifetime. In several country, like in France, abnormal loads regulation was made more flexible in order to avoid long administrative delay to get the permits, and up to some gross vehicle weight limits, the permit can be obtained very easily and quickly on-line through Internet. Some routes are allowed to different classes (1 to 3 in France) of abnormal loads, up to 120 t. Before labelling a route for a given class, all the sensitive bridges should be checked. In 2017, the prefect of Normandy asked to open the bridge of Normandy to the class 3 abnormal loads (120 t). The bridge concessionaire and the Ministry of Transport appointed IFSTTAR and a consulting company (Quadric) to perform some assessment of the impact of these abnormal loads on the bridge orthotropic deck lifetime in fatigue. The paper will present some of the sensitive bridges and details, a quick review of abnormal loads or load models, the trend of heavy vehicle weight limits in the EU, and then the impact of these loads on existing bridges. A special focus will be done on the study carried out for the fatigue of Normandy bridge under current and abnormal traffic loads, and how the abnormal loads can reduce the bridge lifetime. These results are useful for the decision makers to take the final decision on abnormal load authorization
