Research Article
Random-Parameter Multivariate Negative Binomial Regression for Modeling Impacts of Contributing Factors on the Crash Frequency by Crash Types
Table 9
Zero-inflated multivariate negative binomial model estimation results.
| | Variables1 | No.2 | Rear-end estimate (t-stat) | Bumping-guardrail estimate (t-stat) | Other estimate (t-stat) | Noncasualty estimate (t-stat) | Casualty estimate (t-stat) |
| | Constant | 5 | 0.0433 (0.27) | 0.501 (3.07) | −0.527 (−2.11) | −0.0191 (−0.12) | −0.430 (−1.13) |
| | Traffic characteristics | | Interchange | 3 | —3 | — | −0.422 (−2.91) | −0.164 (−1.95) | −0.601 (−2.55) | | Black spots | 5 | 1.057 (11.06) | 0.859 (9.77) | 1.276 (7.17) | 1.196 (9.54) | 1.322 (4.88) | | AADT | 4 | 0.0000263 (8.66) | 0.00000936 (3.00) | 0.0000126 (2.52) | 0.0000365 (11.55) | — |
| | Speed characteristics | | 5 | −0.0131 (−3.63) | −0.00812 (−2.38) | −0.0140 (−2.63) | −0.0177 (−4.58) | −0.0161 (−1.85) | | 5 | 0.0114 (3.31) | 0.00828 (2.45) | 0.0109 (2.09) | 0.0119 (3.25) | 0.0237 (2.45) | | 2 | 0.0210 (3.14) | — | — | 0.0272 (3.82) | — | | 4 | −0.0190 (−4.09) | −0.00934 (−2.11) | −0.0182 (−2.67) | −0.0221 (−4.40) | — |
| | Geometric characteristics | | 1 | — | — | — | — | 0.000251 (2.13) | | 2 | 0.000000361 (3.69) | — | — | 0.000000375 (3.63) | — | | 5 | 0.000588 (10.32) | 0.000468 (8.12) | 0.000755 (8.09) | 0.000753 (11.64) | 0.000748 (6.25) | | 1 | — | −0.000133 (−2.48) | — | — | — | | 3 | −0.000357 (−2.51) | — | — | −0.000423 (−2.83) | −0.000588 (−1.76) |
| | Sight characteristics | | 5 | −0.00540 (−2.78) | −0.00633 (−2.86) | −0.0111 (−3.20) | −0.00706 (−3.44) | −0.0135 (−2.51) | | 3 | −0.0860 (−2.13) | −0.105 (−2.57) | — | −0.0878 (−2.06) | — |
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Total number of parameters: 53; log-likelihood: −14352.888; AIC: 29131.777; BIC: 29674.168; :19426.561. |
