A Methodology for Consideration of Pass-By Trips in Traffic Impact Analyses for Shopping Centers

T raffic impact analysis is a common tool for assessing traffic access needs in the vicinity of new and expanding development sites. Considerable attention has been given in recent years to the development and refinement of procedures and data bases to support these analyses. It has been recognized for some time that shopping centers and several other convenience-oriented land-use types (e.g., banks and fast-food restaurants) have slightly different trip characteristics than other use types. A significant proportion of the trips generated by these uses are simply trips diverted from traffic already on adjacent or nearby roadway facilities. Since not all the trips are “new” trips to the facility, it would seem logical that a reduction in the effective trip generation rate would be justified. Several prior studies have collected data on the percentage of trips typically diverted from traffic already on the road.’ -3 Several of these were summarized by Carl Buttke in a paper presented at the National Conference on Site Development and Transportation Impacts in Orlando, Florida, earlier this year.” ~ -dv On the road will be referr~ to asgss-bv tr~. The ~ercentage Qf ~varies by the type and size Of uses reDreSenteQhe tim e of da~, the geographic locat~ and the nature of t~