The road-infrastructure network consists of many structures like bridges, over- and underpasses. Most of them have a concrete superstructure. They are designed with previous standards instead of current codes. Since their design the traffic has changed dramatically which results in more and heavier loads on these structures. When there is doubt if a structure has sufficient resistance against the current loads, a structural assessment is performed. Although the structure already exists, and therefore a lot of information should be available, not everything might be known. The actual (state of the) reinforcement and the dimensions differ from the structural model. Also, the structural model is often simplified too much. Therefore, the actual load distribution is different. In those cases, it is hard to proof that the structural reliability is sufficient, or even when we can proof on paper that the structure is strong enough there can also be doubt by the client or other (internal or external) Civil Engineers. For smaller bridges where a ductile failure behaviour, like bending is governing, a simple proof loading can be useful. In the Netherlands a CROW guideline [1] on proof loading of bridges has been drafted. This guideline is based on different structures with different techniques to apply the loads. The paper describes this guideline based on a recent practical example of a proof load on a concrete bridge. With the proof load we were able to demonstrate sufficient structural safety for the bridge. In the future, we want to incorporate this method into the standards for structural assessment of existing structures and expand the method to brittle failure mechanisms such as shear in concrete.