Influence of Speed Bumps on Hydraulic Efficiency of Grated Inlets

In the context of the growing promotion of sustainable urban mobility policies, traffic calming is one of the main actions adopted by local, regional, and national administrations to support the liveability and vitality of residential and commercial areas through improvements in non-motorists’ safety, mobility, and comfort. Traffic calming is achieved through the implementation of several actions and physical features such as speed bumps. These elements are generally accompanied by surface drainage elements (grated inlets) located upstream. The presence of speed bumps modifies the hydraulic performance of the inlets. This work aimed to evaluate, by experimental tests, the effects produced by the presence of two different speed bumps on two grated inlets commonly used in Barcelona. The results indicate that the hydraulic efficiency of grated inlets located upstream of speed bumps increases with respect to conventional situations (without speed bumps). These increments are relevant (up to 60%) for flat areas and streets with longitudinal slopes of up to 4–6%, but can be neglected for steep roads (more than 6%). The increase in grate inlet hydraulic performance means modifications in terms of inlet spacing, with significant economic savings for local administrations in charge of the design, implementation, and maintenance of surface drainage systems.