Research Article
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 R2 | 0.1954 | | Number of observations | 898 | |
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