TITLE:
Considerations on the Use of Approximations to Estimate Freight Demand on the Basis of a Single Explanatory Variable with Non-Linear Functional Forms and Generalization to Statistical Modelling
AUTHORS:
Jesus Gonzalez-Feliu
KEYWORDS:
Urban Economics, Freight Trip Generation, Freight Generation, Functional Form, Exponential Transformation, Data Estimation, Category Aggregation, Accuracy Assessment
JOURNAL NAME:
Theoretical Economics Letters,
Vol.14 No.6,
November
13,
2024
ABSTRACT: This paper presents two sets of considerations on the use of approximations to estimate freight trip generation (FTG) and freight generation (FG) rates, based on a single variable. Following recent developments in aggregation approximations for the use of non-linear functional forms in FTG models related to employment, an extension to FG models with a single variable (employment or area) is made. Furthermore, the deployment and application of such approximations to category-based exploratory variables (and not purely quantitative) are addressed. Additionally, to extend these models to FG, the suitability and possible approximations of the exponential function via a polynomial transformation using Taylor series are proposed. Moreover, an analysis of its accuracy using an error analytical assessment. Finally, applicability and generalization issues of the proposed work are addressed, and a general iterative modelling framework is formalized and discussed. This paper builds on previous works on freight demand modelling and proposes methods and estimates that can be used in situations where data disaggregation is lacking, offering complementary analyses to those works that provide a comprehensive view of the main transformable functional forms.