I A Study of Pass - ByTrips Associated with Retail Developments

K ey elements of any new land develo~ment are traffic circulation in and around the site and the potential impact the development may have on the existing street system. Traditionally, the evaluation of these impacts is a four-part process: determining the amount of traffic generated by the site, estimating the origins and destinations of people using the site, assigning traffic to the surrounding street system, and analyzing the traffic operation as a result of this additional traffic. Improvements or modifications to the street system are then determined if necessary. A point of continual disagreement between developers and agencies responsible for reviewing new construction is the amount of traffic generated by the site. The Institute of Transportation Engineers’ Trip Generation provides typical trip generation rates for most types of developments.’ The traffic generated by a development is estimated by determining the development’s size (gross leasable area [GLA], number of acres, number of employees, etc.) and multiplying this by a trip generation rate for that particular use. Although these rates are generally accepted, traffic engineers agree that there should be some allowance for pass-by traffic-that is, trips that come directly from the traffic stream passing the development, that would be on the road whether the development was there or