Estimation of Annual Routine Maintenance Cost for Highway Tunnels

Table 5

Grouped ridge regression.

Variables	Shanbei			Guanzhong			Shannan
		t			t			t
Constant	0.715	0.414	0.69	−30.227	−2.168	0.053	6.686	7.33	0.000
lnAge	0.706	2.645	0.029	0.776	2.028	0.068	0.166	0.783	0.456
lnAADT	0.076	0.787	0.454	1.146	2.097	0.06	−0.306	−5.151	0.001
PTT	0.3	0.537	0.606	−9.951	−0.754	0.467	1.353	0.706	0.5
PSLT	0.11	0.167	0.871	0	0	0	−27.502	−8.038	0.000
PLT	−1.54	−2.029	0.077	1.561	1.757	0.107	−3.844	−4.706	0.002
PMLT	0.476	0.374	0.718	4.023	1.757	0.107	−2.463	−4.993	0.001
lnNVF	0.042	0.111	0.914	5.534	1.757	0.107	−0.284	−5.685	0.000
R^2	0.693			0.647			0.894
F	2.575			3.365			9.615
	0.104			0.039			0.002