Methodology to Evaluate Cost and Accuracy of Parking Patrol Surveys

Patrol surveys are frequently used to estimate average parking duration. However, error in estimating is unavoidable and yet unpredictable. It is, therefore, hard for surveyors to decide on survey budgets; lower ones may generate unusable results and higher ones are costly. Therefore, a method to evaluate and improve survey accuracy without increasing (and possibly even lowering) cost could be highly beneficial. In this paper, an analytical model is built to determine the effects of survey budget on survey accuracy in a systematic and generalized way. The relationship between the survey budget, the estimated average parking duration (i.e., the survey result), and the survey error is illustrated through dimensional analysis. On the basis of this analysis, objective criteria are found to evaluate patrol surveys, a budget test is provided to find the optimal survey budget, and a correction method is proposed to improve survey accuracy. Moreover, simulations are run on the basis of more realistic assumptions, so that the conclusions from the analytical model can be extended to real life situations. The model is well validated with real parking data. An example application is also provided that illustrates how to use the proposed approaches to choose a survey budget and to improve survey accuracy. It is hoped that this study will help surveyors to better understand patrol surveys and obtain high-quality results, while keeping costs to a minimum.