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Parking Management.Strategies, Evaluation and Planning <br /> Victoria Transport Policy Institute <br /> Now Much Is Optimal? <br /> Optimal parking supply is the amount that motorists would purchase if they paid all costs <br /> directly and had good parking and transport options. But conventional planning practices <br /> reflect an assumption that it is desirable to maximize parking supply and minimize user <br /> charges. They consider parking management a measure of last resort,to be applied only <br /> where it is infeasible to expand supply. <br /> Conventional planning determines how much parking to provide at a particular site <br /> planners based on recommended minimum parking standards published by various <br /> professional organizations. This provides an index or parking ratio used to calculate the <br /> number of spaces to supply at a particular location. These are unconstrained and <br /> unadjusted values,which generally reflect the maximum supply that could be needed. <br /> These standards are often excessive and can usually be adjusted significantly downward. <br /> To appreciate why it is helpful to know a little about how parking standards are <br /> developed. Conventional parking standards are based on parking demand surveys,the <br /> results of which are collected and published in technical reports such as ITE's Parking <br /> Generation. This process implies a higher degree of accuracy than is actually justified. <br /> Fewer than a dozen demand surveys are used to set standards for many land use <br /> categories. The analysis does not usually take into account geographic, demographic and <br /> economic factors that can affect parking demand, such as whether a site is urban or <br /> suburban, and whether parking is free or priced. <br /> These standards err toward oversupply in many ways. They are derived from parking <br /> demand studies that were mostly performed in automobile-dependent locations. They are <br /> generally based on 85th percentile demand curves (which means that 85 out of 100 sites <br /> will have unoccupied parking spaces even during peak periods), an 85th occupancy rate (a <br /> parking facility is considered full if 85%of spaces are occupied) and a 10th design hour <br /> (parking facilities are sized to fill only ten hours per year). Applying these standards <br /> results in far more parking supply than is usually needed at most destinations,particularly <br /> where land use is mixed,there are good travel options,parking is managed for efficiency <br /> or priced. <br /> Most people planning apply parking standards have little understanding of the biases and <br /> errors they contain,and the problems created by excessive parking supply. The <br /> application of generous and inflexible parking standards is often defended as being <br /> conservative,implying that this approach is cautious and responsible. Use of the word <br /> conservative in this context is confusing because it results in the opposite of what is <br /> implied. Excessive parking requirements waste resources,both directly,by increasing the <br /> money and land devoted to parking facilities, in indirectly,by increasing automobile use <br /> and sprawl. Better parking management actually tends to be more conservative overall. <br /> t <br /> 9 <br />