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| Variable category | Variable name | Variable description |
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| Traffic flow variables | up_q | Average upstream detector volume 10−5 minutes before the crash |
| up_v | Average upstream detector speed 10−5 minutes before the crash |
| up_o | Average upstream detector occupancy 10−5 minutes before the crash |
| up_dif_q | Average of the absolute value of the difference in traffic flow in the adjacent lane of the upstream detector 10−5 minutes before the crash |
| up_dif_v | Average of the absolute value of the speed difference between adjacent lanes of the upstream detector 10−5 minutes before the crash |
| up_dif_o | Average of the absolute value of the difference in adjacent lane occupancy of upstream detectors 10−5 minutes before the crash |
| down_q | Average downstream detector volume 10−5 minutes before the crash |
| down_v | Average downstream detector speed 10−5 minutes before the crash |
| down_o | Average downstream detector occupancy 10−5 minutes before the crash |
| down_dif_q | Average of the absolute value of the difference in traffic flow between adjacent lanes of downstream detectors 10−5 minutes before the crash |
| down_dif_v | Average of the absolute value of the speed difference between adjacent lanes of the downstream detector 10−5 minutes before the crash |
| down_dif_o | Average of the absolute value of the difference in adjacent lane occupancy of downstream detectors 10−5 minutes before the crash |
| dif_q | Absolute value of flow difference between upstream and downstream detectors 10−5 minutes before the crash |
| dif_v | Absolute value of speed difference between upstream and downstream detectors 10−5 minutes before the crash |
| dif_o | Absolute value of upstream and downstream detector occupancy difference 10−5 minutes before the crash |
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| Weather variables | dewp | Dew point (°C), take the value 1 (≤10); 2 (10–15); 3 (15–20); 4 (≥20) |
| vis | Visibility (km), taking values 1 (<1); 2 (1–5); 3 (5–10); 4 (≥10) |
| prep | Rainfall (mm), taking values 1 (0–5); 2 (5–10); 3 (≥10) |
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| Road features | width | Road width (m) |
| length | Upstream and downstream detector distance (km) |
| curve | Whether it is a curve segment, takes the value 1 (curve segment); 0 (not a curve segment) |
| ramp_up | Number of on-ramps between upstream and downstream detectors |
| ramp_down | Number of down-ramps between upstream and downstream detectors |
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| Time features | weenkend | Whether it is a weekday, takes the value 1 (weekend); 0 (weekday) |
| hour | The time corresponding to the traffic flow data, taking values of 0 (0–1); 1 (1–2); 2 (2–3); 3 (3–4); 4 (4–5); 5 (5–6); 6 (6–7); …; 22 (22–23); 23 (23–24) |
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