Abstract
The gravity law has been documented in many socioeconomic networks, which states that the flow between two nodes positively correlates with the strengths of the nodes and negatively correlates with the distance between the two nodes. However, such research on highway freight transportation networks (HFTNs) is rare. We construct the directed and undirected highway freight transportation networks between 338 Chinese cities using about 15.06 million truck transportation records in five months and test the traditional and modified gravity laws using GDP, population, and per capita GDP as the node strength. It is found that the gravity law holds over about two orders of magnitude for the whole sample, as well as the daily samples, except for the days around the Spring Festival during which the daily sample sizes are significantly small. Accordingly, the daily exponents of the gravity law are stable except during the Spring Festival period. The results also show that the gravity law has higher explanatory power for the undirected HFTNs than for the directed HFTNs. However, the traditional and modified gravity laws have comparable explanatory power.
Highlights
Technological improvement and economic development promote the rapid growth of transportation systems globally and nationwide
We find that the daily networks around the Chinese New Year (5 February 2019) do not exhibit the gravity law
The data for the dates during 1 February 2019 to 9 February 2019 are excluded because their corresponding transportation networks do not exhibit the gravity law
Summary
Technological improvement and economic development promote the rapid growth of transportation systems globally and nationwide. Inspired by Newton’s law of gravity in physical sciences, gravity has been observed in human migration and mobility behavior [1,2,3,4,5,6,7], international trade flows [8,9,10,11,12,13,14,15,16,17], mobile phone communication flows [18,19,20,21,22,23], and so on Some of these studies investigated the power-law decay of the flow with respect to the distance, while most others considered node strengths. As far as highway network is concerned, Jung, Wang and Stanley investigated the Korean highway network between the 30 largest cities [24] They found that the traffic between two cities is positively proportional to the populations and negatively proportional to the distance, fitting exactly the traditional gravity law over two orders of magnitude. We consider M to be GDP (G), population (P) and per capita GDP (G/P), respectively
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