Variable

No injury accidents

Injury or fatal accidents

Parameter

t-statistic

Parameter

t-statistic

Zero-inflated Poisson (ZIP) model. Poisson part

Constant

0.8001

8.32

−0.559

−1.62

Passenger car volume

0.00022

10.80

−0.00012

−1.53

Heavy vehicle volume

0.00014

3.57

−0.00015

−0.86

Light non-passenger car vehicle volume

0.00041

10.84

0.00076

5.48

Traffic speed

0.00392

5.04

0.0021

0.56

Number of lanes

0.1012

4.34

−0.0008

−0.02

Number of horizontal curves

0.2317

15.30

0.5012

11.88

Number of access roads

0.0939

12.73

0.1075

3.59

Zero-inflated Negative binomial (ZINB) model. NB part

Constant

0.2718

0.78

−1.2654

−4.15

Passenger car volume

0.00028

4.12

−0.00012

−1.42

Heavy vehicle volume

0.00009

0.67

−0.00017

−1.32

Light non-passenger car vehicle volume

0.00064

5.09

0.0011

7.17

Traffic speed

0.0084

3.84

0.0130

4.42

Number of lanes

0.0569

0.90

-0.0991

−1.31

Number of horizontal curves

0.3031

6.51

0.4467

8.69

Number of access roads

0.1170

5.33

0.0656

2.41

Dispersion parameter

0.7650

13.12

0.6535

7.14