Table 4.
Six-Minute Segments of Video Recordings Judged to Show a Drowsy Driver, According to the Time of Day and Driving Schedule.*
| Driving Schedule | 7 a.m. to 6:59 p.m. | 7 p.m to 6:59 a.m. | Total | |||
|---|---|---|---|---|---|---|
| NO. OF SEGMENTS | PERCENT | NO. OF SEGMENTS | PERCENT | NO. OF SEGMENTS | PERCENT | |
| All schedules | ||||||
| Drowsy driver | 343 | 2.19 | 1,646 | 12.06 | 1,989 | 6.79 |
| Total | 15,660 | 13,650 | 29,310 | |||
| Steady day | ||||||
| Drowsy driver | 53 | 1.07 | 47 | 2.63 | 100 | 1.49 |
| Total | 4,940 | 1,785 | 6,725 | |||
| Advancing night | ||||||
| Drowsy driver | 91 | 2.08 | 222 | 8.04 | 313 | 4.38 |
| Total | 4,385 | 2,760 | 7,145 | |||
| Steady night | ||||||
| Drowsy driver | 151 | 4.79 | 739 | 16.37 | 890 | 11.61 |
| Total | 3,150 | 4,515 | 7,665 | |||
| Delaying evening | ||||||
| Drowsy driver | 48 | 1.51 | 638 | 13.90 | 686 | 8.82 |
| Total | 3,185 | 4,590 | 7,775 | |||
*
The total number of six-minute segments of driving for each entry in the table was used as a denominator. Since the video recordings were sampled every 30 minutes, we estimated the required number by counting, for each entry in the table, the number of these 30-minute sampling periods that occurred while the truck was moving at a normal speed (as opposed to being parked or stopped) and multiplying this number by 5, since 30 minutes equals five 6-minute segments. According to these calculations, there were 29,310 six-minute segments during which a driver could have been judged to be drowsy while driving.