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;.' Princiole No.8: Parkinq Lot Size RECOMMENDED PRACTICE The amount of impervious cover created by parking lots can be reduced in three basic ways. Communities should first evaluate whether their standard parking stall dimensions are too spacious, and if so, consider shaving six inches or a foot off of their length and width. Second, communities may wish to amend their parking codes to require that a fixed percentage of all parking stalls (e.g., 15 to 35%) be dedicated for compact cars; with correspondingly smaller stall dimensions. Compact parking stalls create up to 30% less impervious cover than stalls for larger cars. Increasing the percentage of compact car parking stalls can lead to smaller parking lots, less impervious cover, and reduced construction and maintenance costs. Third, communities may want to require designation of spillover parking areas for larger parking lots and promote the use of alternative paving materials in these areas. Pervious materials such CIS permeable pavement, grass pavers, grass and gravel, are usually less durable than traditional paving materials, and are appropriate for less traveled spillover parking areas. Pervious paving materials can infiltrate stormwater runoff while simultaneously providing a stable travel pathway. PERCEPTIONS AND REALITIES ABOUT PARKING LOTS There are impediments to changing the way parking lots are constructed. First, there is a perception that today's cars and trucks won't fit into smaller parking stalls. Second, there is a reluctance to use pervious materials due to expense, potential confticts with the Americans With Disabilities Act, uncertainties about long-term performance and durability. These impediments are summarized in Table 8.1 and are further addressed in the following discussion. Are Larger StaLLs Needed for Sport UtiLity Vehicles? One argument against making parking stalls smaller is that to day's consumers are buying larger vehicles - in particular, sport utility vehicles (SUVs), mini-vans, and 4 x 4 trucks. Since 1970, SUV sales have climbed by 47% in the U.S., and presently account for about 25% of the sales of the big-three auto makers (AAMA, 1997). It is important to keep in mind that most sUV's are less than 7 feet wide and can comfortably fit into a standard space. With a few exceptions, most of the size of SUV is vertical - they stand taller than sedans, but are often not much wider or longer than a full-size car. In fact, many SUV models are actually smaller than a typical car (e.g., Jeep Wranglers). ALternative Paving Issues Alternative paving materials can make sense in many parking lot designs, but accessibility, site conditions, and long-term performance need to be carefully considered. Accessibility In general, conventional paving material should be IJsedin handicapped parking areas and on public pathways such as sidewalks to ensure a smooth surface for travel. Note that the City of Olympia has found thafUNI Eco-Storie, an alternative pavement option, does comply with the ADA (Wells, 1997), providing a uniform travel surface. - 75 -