Estimation of Annual Routine Maintenance Cost for Highway Tunnels

Table 1

Dependent and independent variables.

Variables			Units	Variable type
Dependent variables			Cost/m/lane in 2016 FY RMB	Continuous
Independent variables	District	Shanbei = 1, Guanzhong = 2, Shannan = 3	—	Categorical
	Time	Age (the opening years of tunnels)	year	Continuous
		∑ESAL	year	Continuous
	Traffic	AADT	day	Continuous
		ESAL	year	Continuous
		AADTT	day	Continuous
		PTT	—	Continuous
	Tunnel parameters	NT	—	Continuous
		PET (PSLT, PLT, PMLT, and PST)	—	Continuous
		NVF	A full set of ventilation facilities	Continuous
		NLF	A full set of lighting facilities	Continuous