The capacity of existing solid slab bridges in the Netherlands is under discussion for two reasons: 1) the increased traffic loads and volumes and 2) the fact that the majority of the existing bridges were built before 1976, and are thus reaching the end of their original life span. Upon assessment according to the governing codes, a large number of slab bridges are found to be shear-critical. However, the shear capacity as prescribed by the codes is based on experiments on beams in shear. Slabs subjected to concentrated loads (such as truck wheel load) are assumed to have additional capacity as a result of transverse load redistribution. This thesis studies the capacity of slabs under concentrated loads close to supports. A literature review, resulting in a slab shear database with 215 experiments from the literature, is used to study the mechanisms at work in one-way and two-way shear. For this research, 156 experiments were carried out on 38 half-scale bridge deck specimens. The experimental results are studied by means of a parameter analysis. To determine the capacity of slabs in shear subjected to concentrated loads, two methods are proposed in the thesis: 1) the Modified Bond Model, a new theory to determine the capacity of slabs subjected to concentrated loads; and 2) by using a code extension proposal that results from probabilistic calculations following the safety philosophy of the Eurocodes. Finally, the link to the assessment practice is made by formulating recommendations, improving the Quick Scan assessment tool of the Ministry of Infrastructure and the Environment, and then applying this to cases of existing solid slab bridges.