| Explanatory Variable | Importance % |
| Rd_char | 42% |
| Rdsurf | 4.3% |
| AADT | 27.9% |
| Weather | 6.7% |
| Light | 4.2% |
| Drv_age | 5.2% |
| Drv_sex | 2.0% |
| Vehtype | 5.1% |
| Sec_leng | 2.6% |