I'm preparing a traffic study for the proposed 25,700 square foot Lunds grocery/liquor/pharmacy store at Hennepin/12th in downtown Minneapolis. We would typically use the Institute of Transportation Engineers' reports (industry standard data sets) to help us forecast the amount of parking needed at the site as well as the amount of traffic that will be generated.
Based on discussions with the city, we think the standard data sets may overestimate the traffic/parking needs of the downtown grocery store since the existing data sets are largely based on suburban locations. Lunds has another urban grocery store on the edge of downtown Minneapolis on Central Avenue. Here is the data table from a p.m. peak hour study of that existing urban grocery store (Download Parking-Trip Generation at Central Lunds).
We found slightly lower peak hour trip generation rates and significantly lower peak period parking rates compared to the Institute of Transportation Engineers' reports. This makes sense at an urban grocery store. They still have a good volume of customers, but those customers are making a quick stop in for a few items and then getting out as fast as possible. At more suburban grocery store locations, we'd expect patrons to buy more and stay longer. Suburban grocery stores aren't as well set up for convenience stops.