Trip generation characteristics of large-format retail development sites in Auckland

This paper investigates the period peak trip generation rates and trip type proportions for two large format retail activities. Transportation assessments of proposed retail developments typically involve application of generic trip rates to assess traffic effects to a road network, often with little, if any regard given to the nature of the trips that are generated. In particular, not all generated trips will be new trips on the road network. Rather, a proportion will exist as pass-by and linked diverted trips (secondary trips). By not considering these secondary trips, transportation assessments have tended to be overly conservative when examining road network effects, thereby resulting in over-design of traffic management mitigation measures and hence higher establishment costs for the developer. However, there is little data that pertains to trip type proportions for large-format retail developments. In this study, interview and traffic count surveys were undertaken at a supermarket and a home improvement warehouse to determine trip type proportions of these activities in a New Zealand context. It was found that a high proportion of secondary trips exist, being in the range of 57-67 percent.