The Impact of Truck Proportion on Traffic Safety Using Surrogate Safety Measures in China

Table 5

k-means clustering analysis in different periods.

Different periods (min)	Clustering & testing	Classification	85%V–15%V	Variation coefficient
5	Initial clustering center	1 (dangerous)	68.957	0.394
		2 (safe)	11.923	0.090
	Final cluster center	1 (dangerous)	50.715	0.276
		2 (safe)	32.290	0.172
	The value of split point		41.503	0.224
	ANOVA	F	1525.788	2388.247
		Sig.	0.000	0.000
10	Initial clustering center	1 (dangerous)	64.489	0.348
		2 (safe)	12.457	0.095
	Final clustering center	1 (dangerous)	51.001	0.273
		2 (safe)	33.252	0.175
	The value of split point		42.127	0.224
	ANOVA	F	945.529	1733.678
		Sig.	0.000	0.000
15	Initial clustering center	1 (dangerous)	64.067	0.371
		2 (safe)	14.971	0.136
	Final clustering center	1 (dangerous)	51.266	0.271
		2 (safe)	34.077	0.174
	The value of split point		42.672	0.223
	ANOVA	F	626.887	1129.481
		Sig.	0.000	0.000