retail traffic study--parking area

I have gas/convenience store that isup for review by the local planning board. The are concerned abut stacking from the pumps to the street. We have about 100 feet from the fist pump to the street, with two pump islands, each set to contain two (dual sided) pumps each, for a total of 8 pumping stations. I am looking for peak hour data (tables--ie so and so many expected cars per peak hour based on number of pumps, square footage of building, so on) of some kind that will show that we have enough room for folks to get there gas, and not back up to the street. We also have 22 additional parking areas for those buying other goodies. The population is about 3500 people per sq mi within the area, with mostly just residences and light retail/commercial in the immediate vicinity, with fairly heavy commuter traffic on the adjoining street (not accesible from site). Basically, we want to keep it simple, use some historic data for similar facilities. We think we are OK since the client's other place, with a similar lot layout, on a much busier road, has had no trouble with stacking. Thanx.