Permeable paving systems are surfaces that are able to absorb storm water, thereby minimizing and delaying surface water runoff, while reducing the amount of some pollutants. After storm events, the water either trickles through the permeable surfaces itself (e.g. porous asphalt, permeable concrete), or through gaps or funnels between pavers. Water is then temporarily stored in the underlying stone layer and infiltrates into the soil or to an additional drainage layer that conveys water to the sewage system. While solutions like permeable concrete provide a homogenous surface, others, like vegetated grid pavers, can increase the share of substrate and support vegetation.