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PRINCIPLE No.8 Reduce the overall imperviousness associated with parking Lots by providing compact car spaces, minimizing stall dimensions, incorporating efficient parking lanes, and using pervious materiaLs in spilLover parking areas. Source: WeLls 1995 CURRENT PRACTICE The size of a parking lot is driven by stall geometry, lot layout, and, as discussed in Principle No.6, parking ratios. A parking space is composed of five impervious components, of which the stall is only one part. The five components include: · the overhang at the edge of the stall (beyond the car) · a narrow curb (or curb stop); · the parking stall; · the parking aisle that aLLows access to the staLL; and · a share of the common impervious area (e.g., fire lanes, entrances, and traffic lanes). The impervious area associated with each parking space is more than double the area of an individual stall (see Figure 8.1). In most local parking codes, stall size can range from 162 to 185 square feet-often 10 feet wide and 19 feet long. Another component of lot layout is the internal geometry or traffic pattern. Two-way traffic aisles require greater widths than one-way aisles. One-way aisles used in conjunction with angled parking stalls can significantly reduce the overall size of the parking lot. Parking lots are the largest component of impervious cover in most commercial and industrial zones, but conventional design practices do little to reduce the paved area in parking lots. For example, many parking codes require a standard parking stall dimension that is geared to larger vehicles. Communities seldom allow smaller parking spaces that can handle compact cars, despite the fact that these smaller cars comprise 40 to 50% of all cars on the road (ITE, 1994a). In addition, local construction specifications for parking lots specify an impermeable asphalt or concrete surface. Use of more permeable surfaces, such as grass pavers and porous concrete, is usually frowned upon by reviewing authorities. Most parking codes also do not distinguish between regular parking areas that are used most of the time and spillover parking, which is used for a few days per year. Spillover parking areas are often the best locations to use more permeable paving options. --' - 73 -