Evolution of the China Railway Express Consolidation Network and Optimization of Consolidation Routes

Table 3

Parameters and variables used in the CRECN model.

Symbol	Definition
Sets
	Set of CRE origin nodes, indexed by
	Set of CRE consolidation centers, indexed by
	Set of CRE corridor gateways (i.e., ports of exit between China and Europe), indexed by
	Set of Destination nodes, indexed by , which is Moscow
Parameters
	The unit setup cost of the consolidation centers
	The unit value of time
	Maximum daily cargo-handling ability of the consolidation center
	Rail distance between nodes and
	Annual freight volume of node
	Cargo cost (CNY/t-km) before consolidation
	Cargo cost (CNY/t-km) after consolidation
Decision variables
	Binary variable. If node j is selected as a consolidation center, then ; otherwise,
	Binary variable. If origin nodes consolidates to node , then ; otherwise,
	Binary variable. If corridor gateway m is selected as an exit point in the route from consolidation center to destination , ; otherwise,