Estimation of Crash Severity on Mountainous Freeways in Chongqing

Table 2

Results of partial proportional odds model.

Parameter	Explanatory variable	Coefficients
Beta	Time
	2 = 06:00~12:00	−0.0772	2.49
	3 = 12:00~18:00	−0.1989	2.78
	4 = 18:00~24:00	0.0551	2.43
	Reference: 1 = 00:00~06:00
	Season
	2 = summer (May–Oct.)	0.5443	3.56
	3 = autumn (Nov.)	0.6246	3.28
	4 = winter (Dec.–Feb.)	−0.0411	2.39
	Reference: 1 = spring (March-April)
	Involvement of trucks	0.4982	3.88
	Accident form
	2 = sideswipe	−0.6413	3.59
	3 = turnover	0.6754	3.7
	4 = rear-end	0.0018	2.31
	Reference: 1 = with fixed object
	Violation of speed limit	2.4455	9.46
	Maximum driving experience of at-fault driver
	1–3 years	−0.2072	2.68
	>3 years	−0.5387	3.48
	Reference: ≤1 year
	Weather
	Sunny	−0.2808	2.83
	Rainy	−1.2157	4.23
	Snow	−2.2874	4.1
	Foggy	1.7105	3.89
	Reference: cloudy
	Section form
	Toll station	−13.8105	2.33
	Service area	−0.5278	2.97
	Upgrade	−1.7255	3.47
	Downgrade	1.9346	5.48
	Ramp	2.1329	3.98
	Curve	1.0979	4.69
	Construction area	−0.0832	2.44
	Bridge	0.7885	4.02
	Tunnel	0.1135	2.57
	Reference: straight
Alpha	Constant 1	−2.6414	−3.10
	Constant 2	−3.9607	−4.55
Summary statistics	Log likelihood	−232.1337
	Pseudo R^2	0.1954
	Number of observations	898