Table 5.

Characteristics of work periods by sleep pattern clusters.

Cluster	Avg. work period (h)	Avg. driving hour (h)	Avg. driving %	Avg. at-work hour* (h)	Avg. at-work %*
1	10.0 (3.1)	6.8 (2.7)	68.6 (19.5)	9.4 (2.7)	95.1 (9.1)
2	9.4 (3.1)	6.8 (2.4)	73.4 (15.7)	9.1 (2.9)	97.2 (7.1)
3	11.0 (3.0)	7.7 (2.7)	70.8 (17.5)	10.3 (2.7)	93.6 (10.0)
4	12.1 (3.4)	8.8 (2.9)	73.7 (17.8)	11.2 (3.3)	92.7 (10.2)

Numbers in parenthesis are standard deviations of the data.

Abbreviation. Avg. = Average; h = hours.

^*At-work includes driving truck, heavy work, and light work (i.e., activity codes 1, 2, and 6).