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

Table 3

The relationship between basic traffic flows in the correlation analysis.

Variables (truck proportion) (min)	Basic parameters (-No-^a)	Mean speed	Traffic volume	Speed difference	Speed standard deviation	85%V–15%V	Variation coefficient	Number of lane changes
5	The correlation	−0.626	−0.216	−0.077	−0.151	−0.156	0.191	−0.039
	Significance (bilateral)	0.000	0.000	0.039	0.000	0.000	0.000	0.295
	.df	732	732	732	732	732	732	732
10	The correlation	−0.647	−0.246	−0.110	−0.181	−0.173	0.193	−0.019
	Significance (bilateral)	.000	.000	.036	0.001	0.001	0.000	0.724
	.df	365	365	365	365	365	365	365
15	The correlation	−0.656	−0.245	−0.085	−0.144	−0.126	0.252	−0.001
	Significance (bilateral)	0.000	0.000	0.181	0.023	0.045	0.000	0.993
	.df	251	251	251	251	251	251	251

a: the cell contains a zero-order correlation (Pearson).