Bi-Objective Optimization for Vehicle Routing Problems with a Mixed Fleet of Conventional and Electric Vehicles and Soft Time Windows

Table 2

Parameter and variable definitions of the model.

Notation	Description
	Fixed cost of vehicle
	Unit energy cost of vehicle
	emission coefficient of energy used by vehicle
	Charge cost per unit of electricity
	Carbon tax
	Waiting cost per unit time
	Delay cost per unit time
	Time window at vertex ,
	Service time at vertex ,
	Demand of vertex ,
	Travel distance between vertices and ,
	Travel time between vertices and ,
	Battery capacity of EVs
	Recharging rate
	Vehicle capacity
	Energy consumption per unit distance when the load of vehicle is
	Decision variable specifying the time of arrival at vertex ,
	Decision variable specifying the remaining load of vehicle when arriving at vertex ,
	Decision variable specifying the remaining battery capacity of EV when arriving at vertex ,
	Binary decision variable specifying whether arc is travelled by vehicle ,