Research on Traffic Congestion Based on System Dynamics: The Case of Chongqing, China

Table 1

Determination of system boundaries.

System category	Specific variables
Residents’ travel	Private car ownership
	Private car travel
	Private car growth rate
	Private car scrap rate
	Bus ownership
	Bus growth rate
	Other motor vehicle ownership
	Other motor vehicle growth rate
	Related governance policy
Urban logistics	City freight volume
	Urban freight growth rate
	Car ownership
	Freight car trips
	Urban freight growth
	Related governance policy
Others	Permanent residents
	Resident population growth rate
	Total household registration population
	Household registration population growth rate
	Total car purchase price
	Car tax
	Fuel cost
	Fuel cost growth rate
	Parking fee
	Total road area of the city
	Average road area
	Annual growth rate of urban road area
	City GDP
	GDP growth rate
	NO2 stock
	Each vehicle emits NO2 per year
	Motor vehicle contribution rate to NO2 emissions