Statistical Safety Performance Models considering Pavement and Roadway Characteristics
Table 4
Estimated coefficients of fitted count regression models.
Poisson
NB
HNB
ZINB
Truncated NB
Zero hurdle
NB
Zero inflated
(2) Ln_Lgth
0.566
0.560
0.510
0.359
0.568
(0.008)
(0.048)
(0.040)
(0.059)
(0.037)
(3) Ln_AADT
1.401
1.275
1.231
0.452
1.217
(0.012)
(0.061)
(0.044)
(0.070)
(0.039)
(4) Lq_MPD
0.082
0.404
−0.701
0.744
(0.023)
(0.139)
(0.161)
(0.188)
(5) Av_Frict
−0.004
−0.010
−0.017
(0.001)
(0.006)
(0.008)
(6) Av_Grad
0.275
0.231
0.172
0.142
0.215
(0.011)
(0.066)
(0.062)
(0.087)
(0.058)
(8) Ln_Lgcv
0.040
0.040
0.034
0.045
(0.002)
(0.013)
(0.011)
(0.011)
(9) PvType2
−0.541
−0.247
−0.333
−0.391
(0.022)
(0.133)
(0.118)
(0.103)
PvType3
−0.176
−0.186
−0.184
−0.324
(0.017)
(0.093)
(0.092)
(0.074)
(10) RrlorUrb2
0.274
0.168
0.270
0.247
(0.018)
(0.098)
(0.089)
(0.083)
(11) ExsMdn2
−0.530
−0.645
−1.027
(0.041)
(0.168)
(0.219)
(12) ExsShd2
−1.463
−1.388
−1.034
−2.487
−1.190
(0.033)
(0.199)
(0.148)
(0.524)
(0.145)
(13) RnkIRI2
0.012
0.051
(0.045)
(0.174)
RnkIRI3
0.264
0.319
(0.045)
(0.165)
(14) RnkRut2
−0.150
(0.042)
RnkRut3
−0.175
(0.043)
Intercept
−14.996
−13.165
−13.876
−2.368
−13.521
−1.723
(0.146)
(0.761)
(0.565)
(1.045)
(0.492)
(0.169)
Observations
1,811
1,811
1,811
1,811
No. of parameters
16
12
21
12
No. of predicted zeros
142
585
625
634
AIC
46,152.6
10,792.8
10,586.2
10,661.7
BIC
46,240.6
10,858.9
10,701.7
10,727.7
Log likelihood
−23,060.3
−5,385.4
−5,272.1
−5,318.8
Note. 1. Significance indicated with -value: < 0.1, < 0.05, and < 0.01. 2. Abbreviations of variables are consistent with those in Table 2. Indicator variables were compared to the first category; for example, PvType2 indicates segments with JCP surface compared to AC surface.
