Table 4 Model results of mixed logit with heterogeneity in means and variance in single-vehicle crashes involving driving exceeding the speed limit in the US, 2016-18.
Variable* | Parameter estimates | t-stat. | Marginal Effects | ||
|---|---|---|---|---|---|
No injury | Minor injury | Severe injury | |||
Constant [SI] | -2.517 | -3.78 | |||
Random parameter (normally distributed) | |||||
Constant [MI] (Standard deviation of random parameters) | -4.684 (11.541) | -2.25 (2.80) | |||
Heterogeneity in mean of random parameter | |||||
Constant [MI]: Restraint usage indicator (1 if drivers were restrained in the crash, 0 otherwise) | -0.651 | -1.66 | |||
Heterogeneity in variance of random parameter | |||||
Constant [MI]: Clear weather indicator (1 if crashes occurred in the clear weather, 0 otherwise) | 0.423 | 3.51 | |||
Temporal characteristics | |||||
Time between 12 AM to 5:59 AM indicator (1 if crashes occurred between 12 AM to 5:59 AM, 0 otherwise) [MI] | -2.548 | -2.04 | 0.0076 | -0.0171 | 0.0095 |
Crash characteristics | |||||
Vehicle running off the roadway indicator (1 if a vehicle ran off the roadway, 0 otherwise) [SI] | 0.776 | 4.53 | -0.0743 | -0.0083 | 0.0827 |
Tree indicator (1 if crashes involving with trees, 0 otherwise) [SI] | 1.164 | 7.23 | -0.0244 | -0.0037 | 0.0281 |
Vehicle characteristics | |||||
Motorcycle involvement indicator (1 if crashes involving motorcycle, 0 otherwise) [NI] | -3.208 | -4.26 | -0.0042 | 0.0002 | 0.0040 |
Displacement ranging from 5000 to 10,000 cc indicator (1 if crashes involved with the vehicles for displacement from 5000 to 10001 cc, otherwise) [MI] | -4.794 | -2.06 | 0.0044 | -0.0098 | 0.0054 |
Newer vehicle indicator (1 if crash involved with vehicles that were manufactured within 5 years from the year of collision, 0 otherwise) [MI] | 2.836 | 2.17 | -0.0114 | 0.0243 | -0.0129 |
Vehicles manufactured by Chevy and Ford indicator (1 if crashes involved with vehicles manufactured by Chevrolet and Ford, 0 otherwise) [MI] | -2.045 | -1.67 | 0.0055 | -0.0113 | 0.0058 |
Roadway characteristics | |||||
Non-interstate indicator (1 if crashes occurred on non-interstate, 0 otherwise) [SI] | -0.366 | -1.81 | 0.0348 | 0.0041 | -0.0388 |
Two-way undivided roadway indicator (1 if the crashes occurred on two-way undivided roadway, 0 otherwise) [SI] | 0.475 | 3.52 | -0.0273 | -0.0034 | 0.0307 |
Straight roadway indicator (1 if crashes occurred on straight roadways, 0 otherwise) [NI] | -0.254 | -1.98 | -0.0180 | 0.0015 | 0.0165 |
Dry surface indicator (1 if crashes occurred on dry surface, 0 otherwise) [NI] | -0.576 | -3.84 | -0.0547 | 0.0040 | 0.0507 |
Wet surface indicator (1 if crashes occurred on wet surface, 0 otherwise) [MI] | 2.136 | 1.73 | -0.0053 | 0.0093 | -0.0040 |
Driver characteristics | |||||
Male driver indicator (1 if male driver involved in crash, 0 otherwise) [SI] | 2.913 | 4.98 | -0.2320 | -0.0271 | 0.2591 |
Female driver indicator (1 if female driver involved in crash, 0 otherwise) [NI] | -3.166 | -5.32 | -0.1047 | 0.0102 | 0.0945 |
Drives age from 35 to 45 years (1 if drivers involved in crashes were between 35 to 45 years old, 0 otherwise) [SI] | 0.323 | 1.73 | -0.0049 | -0.0006 | 0.0055 |
No drinking indicator (1 if drivers involved in crashes were not drinking, 0 otherwise) [NI] | 0.730 | 5.40 | 0.0618 | -0.0058 | -0.0560 |
Non-restraint usage indicator (1 if no restraint was used, otherwise) [MI] | -5.954 | -2.08 | 0.0012 | -0.0063 | 0.0051 |
Restraint usage indicator (1 if restraint used, otherwise) [NI] | 1.841 | 11.98 | 0.1741 | -0.0164 | -0.1576 |
Number of observations | 2299 | ||||
Log-likelihood at zero | -2525.709 | ||||
Log-likelihood at convergence | -2174.635 | ||||
ρ2 = 1 – LL(β)/LL(0) | 0.139 | ||||
