Expressway Usage Pattern Analysis Based on Tollgate Data: A Case Study of the Shandong Province, China

Table 3

Definition of variable.

Variables	Definition	Unit
Road network
	The capacity of road segment , calculated by the lane capacity of the road segment and the number of lanes	pcu/h
	The free travel time of road segment , calculated by dividing the road length by the designed speed limit	mins
	Travel time of road segment	mins
	Traffic flow of road segment	pcu
Trips
	Traffic demand of OD pair from to	—
	Routes of each trip from to , , are road segments in the route	—
Driver source
	Contribution of driver source to segment	pcu
	Major driver sources of segment , , are tollgates in major driver sources of segment	—
	Main driver source in the road network, if node is one major driver source of a segment, plus one, is the road network node corresponding to a tollgate	—
Complex network indicators
	If is origin of a trip, plus one	—
	Closeness centrality, where is the distance between node and node
	Betweenness centrality, , where presents the number of shortest paths between node and node . presents the number of shortest paths between node and node , but those shortest paths must pass through node