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Redwood City Costco Gasoline Expansion ProjE 7.A. - Page 242 August 20,2012 ruye 3v at least 75% of the data does not fit the statistical model, then the relationship between trip generation and the given variable should not be used for predicting future outcomes for trip generation. As can been seen from Figure 10 and 11, trip generation at the Costco Gasoline fuel stations does not have a reasonably direct linear or logarithmic relationship to number of fueling positions or to average daily gallons sold. The logarithmic trend line for trip generation based on fueling positions has an RZ value of only 0.035 (meaning only 3.5% percent of the data fits the model) and the logarithmic trend line for trip generation based on gallons of fuel sold has an RZ value of only 0.19 (meaning only 19% of the data fits the model). Both are well below what would be considered a reasonable or direct correlation for the data. As such, neither number of fueling positions or gallons sold can be considered a reasonable variable or approach for estimating future trip generation. Furthermore, given that we have actual trip counts from traffic count data at the 29 existing Costco Gasoline facilities in Table 9, there is no reason to try an estimate trip generation based on surrogate measures as we have the true data based on traffic counts. Independent variables are used to predict future outcomes for unknown situations or in the lack of other data. For this analysis, we have actual trip counts at the existing Redwood City Costco Gasoline facility (in its current configuration) as well as actual trip count data at over 25 other Costco Gasoline facilities that provide a solid database from which to see the range of possible trip generation numbers for the proposed future configuration. Based on these findings, a range of other methodologies were applied to determine a reasonable yet conservative estimate for the expected increase in trip generation due to the proposed fuel station expansion. Trip Generation Estimate Methodology There are two specific elements that directed the methodology used to prepare a trip generation estimate for the proposed fuel station expansion. The first is that the project is an expansion to an existing fuel station that has been operational for almost 2 years. This creates a very different scenario from evaluating the impacts of a completely new use. Secondly, there are only two existing 5 island Costco Gasoline fuel stations within the continental United States and, therefore, there is a limited sample size upon which to draw for their characteristics. Because of this, detailed and thorough review of trip generation from several approaches was conducted to provide sufficient support and confidence in the evaluation and resulting estimate. To develop the trip generation estimate for the expanded Redwood City fuel station,the following steps were completed: Kittelson&Associates,Inc. Boise,Idaho