| | Vehicle factor group 4 | | Layer | Topics | Rate |
| | Layer 1 | Alignment | Right-curve, right-curve 500 m–1000 m, right-curve 1000 m more, straight | 3% | | Inclination | Uphill, uphill less than 1%, uphill 1% to 3%, uphill 3% more, uphill less than 500 m, flat | 13% | | Cut and fill | Flatness, fill height less than 2 m, fill height 2 m–5 m, fill height 5 m–15 m, cut part less than 10 m, cut part 10 m more | 2% |
| | Layer 2 | Point of occurrence | Main lane | 1/2, 1/3, 1/4, 2/2, 2/3, 2/4, 3/3, 3/4, 3/5, 4/4, 4/5, 5/5 | 11% | | Shoulder | Shoulder, 2/2 | 5% |
| | Layer 3 | Traffic obstacle factors | Non-working section, normal, stopped vehicle | 15% | | Road environment | Dry, wet | 10% | | Main accident cause | Tire damage, brake device defects, problem of device parts | 10% |
| | Layer 4 | Accident type | Single accident, shoulder, shoulder guardrail | 6% | | Vehicle operation just before the accident | Driving, overactive handle, others | 5% | | Main accident type | Vehicle-structure, others | 6% |
| | Layer 5 | Day and night | Daytime, nighttime | 7% | | Weather | Sunny, rainy | 7% |
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