DEFINITIONPorous pavements are a paving system that allows water to infiltrate through the pavement in order to more accurately reflect the pre-development hydrologic cycle
In the realm of stormwater management, porous pavement is considered a structural measure.
Specifically, it is a generic term that includes porous asphalt, porous concrete and modular pavers.
Like a conventional surface, porous pavement consists of a pervious surface course that is typically underlain by washed, uniformly graded coarse aggregate, followed by a a layer of geotextile and finally the un-compacted sub-grade.
The idea is that stormwater enters through the pores in the pavement and is stored in the voids that exist in the layer of aggregate until it can percolate through the natural ground.
Porous pavement is not intended for roadways; it is meant to be used in parking lots, walkways, playgrounds, etc... and other areas where low speeds apply.
A variation of the product has been developed for roadways. Superpave (to put simply, conventional asphalt minus the fines) is used to hasten water runoff from roadways.
AKAPorous Concrete, Porous Asphalt, Porous Pavers, Open-jointed Paving blocks, Open cell paving blocks (gravel, grass etc), Pervious Pavement
PERFORMANCE CRITERIAthe primary measurement for performance is the infiltrative capacity of the pavement. this can be effected over time by the build up of sediment and dirt within the pores of the pavement, but this can be remedied with regular maintenance
ILLUSTRATION
In the parking lot for Nextel at Tecnoparque in Mexico City


Two examples in Germany, open pavers and filter strips under the car
CASE STUDIESHigh Point, Seattle
Kitsap Homebuilders LID Demonstration Project, Bremerton
Williamsburg Prime Outlets, Hampton Roads, Virginia
Arkadien AspergHousing Development, Stuttgart, Germany
ADDITIONAL RESOURCESPorous Pavement Powerpoint(as PDF) for Seattle's Stormwater Seminar Series
case study of an eastern North Carolina permeable pavement:
http://www.box.net/shared/al1h2z7todToronto Guidelines for Greening Parking LotsCity of Seattle Guide for Green Parking LotsPortland Cement Pervious Concrete Pavement: Field Performance Investigation on Parking Lot and Roadway PavementsCurtis Hinman of WSU's survey of porous pavement performance researchMutual Materials'
Eco-Stone Performance Study