01373414

Component

https://doi.org/10.3141/2269-01

http://scholar.google.com...nson&publication_year=2012

The application of a gravity model in freight modeling work on both short-haul and long-haul trips is discussed. A commodity-based gravity model was developed to assess the distribution of freight by long-haul trucks in southeastern Virginia. Although gravity models have been used extensively in transportation studies, little work has been done to address the special characteristics of freight transportation, such as the definition of friction factors and the differences between long-haul and short-haul trips. Results of a recent study of these and similar problems provide valuable insight into freight distribution modeling. A new calibration method that used a genetic algorithm was applied, various commodities were modeled, and the impact of the commodities on the accuracy of the gravity model was studied. Both travel time and travel distance were tested to generate the impedance for friction factors; results showed that for commodity-based long-haul models, travel times were more appropriate for friction factor calculations. In addition, results showed that the gamma function was more suitable than the exponential function for friction factor calculations. Extensive analyses of the causes of variation between observed values and the gravity model outputs are provided. The analyses and conclusions may help modelers better understand characteristics specific to freight transportation and can promote model constructions with greater accuracy and efficiency.

This paper was sponsored by TRB committee AT015(3) CFP - Freight Transportation and Logistics Modeling

01384365

12-2782

English

0000-0002-0790-7794

pp 1-10

2012

Transportation Research Record: Journal of the Transportation Research Board

9780309223102

Print

Figures; References; Tables

Calibration; Commodities; Freight transportation; Genetic algorithms; Gravity models; Haul distance; Physical distribution; Travel time

Freight Transportation; Planning and Forecasting; I72: Traffic and Transport Planning

TRIS, TRB, ATRI

Feb 8 2012 5:12PM

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