I Refinement of Procedures Used for Estimating Pass - By Trip Percentages

P ass-by trips are defined as trips attracted to a particular development from the traffic “passing by” on the adjacent street. Being able to predict and apply pass-by trip percentages as part of a traffic impact analysis allows engineers to more accurately estimate the traffic impacts of a new development on the surrounding street system. Intuitively, it seems reasonable that the higher the adjacent street average daily traffic (ADT) and level of service (LOS), the higher the pass-by percentage. It also follows that there would be a higher pass-by percentage in an office park setting than in a residential one. While we can intuitively agree these relationships exist, there currently are no generally accepted guidelines for estimating pass-by trip percentages. This situation causes problems when a developer and the reviewing agency disagree on appropriate pass-by trip percentages. It is possible, particularly with larger developments, that the difference in passby trip percentages used could result in thousands of dollars in improvements being required of the developer. With this much at stake, it is imperative that we have better procedures for estimating pass-by trip percentages.