Investigation on the Time Factor of CO-Based Emission Factors for Sustainable Development of Urban Tunnels in China

Table 1

The accuracy check level of GM (1: 1) model.

Grades	Grey absolute correlation degree ζ	Relative residual error	Mean square error ratio C	Small probability error P
Level I	0.90	0.01	C ≤ 0.35	P ≥ 0.95
Level II	0.80	0.05	0.35 < C ≤ 0.5	0.8 < P ≤ 0.95
Level III	0.70	0.10	0.5 < C ≤ 0.65	0.7 < P ≤ 0.8
Level IV	0.60	0.20	C ≥ 0.65	P < 0.7