Are Freight Production Models Transferable between Urban and Suburban Areas? Guiding Model Transfer in Geographically Sprawling Indian Cities

Investigating the spatial transferability of freight generation (FG) models is an imperative research need to enable the usage of formerly estimated model parameters in new application contexts with or without the usage of local data. By understanding how to transfer models (and to what extent), planning agencies in large countries like India can save freight survey costs in regions where they lack the institutional capacity and resources. Due to geographically sprawling nature of most of the Indian cities, an important research question regarding transferability is whether the models developed for urban areas can provide accurate estimates of freight activity in the suburban areas or vice versa. This paper aims to provide two solutions to this problem: (i) compare the relative effectiveness of transferability depending up on the direction of transfer and (ii) assess which models can be transferred and which cannot. Data collected from seven cities are used for this study. A set of freight production (FP) models are developed using this data to understand the differential influence of geographical location and industry segment on the model coefficients. The estimated FP models show that suburban establishments exhibit significantly higher FP rates as compared to other establishments. Subsequently, transferability direction and accuracy are determined using standard metrics such as transfer R(2), relative aggregate transfer error and transfer index. The transferability findings will provide actionable insights into development of FP models in regions with data constraints, which is of great value in an era of declining budgets for travel surveys.