Regional Logistics Network Design in Mitigating Truck Flow-Caused Congestion Problems

Table 1

Symbol description.

Symbol	Description (unit)
	Set of nodes in the network
	Set of demand points
	Set of supply centers
	Set of existing roads will not be expanded
	Set of existing roads will be expanded
	Amount of demand point needed (unit: tons)
	Transportation cost per unit of cargoes of road (i, j) (unit: RMB yuan)
	Fixed cost of constructing facilities at node during the planning period (unit: RMB yuan)
	Construction cost per unit of the road based on logistics volume (unit: RMB yuan)
	Expansion cost per unit of the road based on traffic flow (unit: RMB yuan)
	Logistics turnover cost per unit for constructing the facility location i (unit: RMB yuan)
	Capability of the traffic flow on the road (unit: pcu/h)
	Penalty cost for delivery time not between the upper and lower bounds. It is regarded as the loss of opportunity cost because of stock out when delivering commodities. Moreover, it should be designed for the cargoes in societal logistics, such as medical supplies for emergency. (unit: RMB yuan)
	Decision variable is equal to 1 when the facility location is at node ; otherwise, it is 0
	Decision variable, which stands for the freight volume of the road during the planning period, described as the amount of cargo from facility to demand point (unit: t)
	Turnover during the planning period when facility point i is also the candidate for facility location (unit: tons)
	, decision variable, if , then expand the road; otherwise, its value is 0