Table 1.

Score of IDS riders' overwork (Work Burden Index).

Self-conscious symptoms	Working status
	A	B	C	D
I	0 (safety zone)	0 (safety zone)	2 (early warning zone)	4 (dangerous zone)
II	0 (safety zone)	1 (safety zone)	3 (early warning zone)	5 (dangerous zone)
III	0 (safety zone)	2 (early warning zone)	4 (danger zone)	6 (high-risk zone)
IV	1 (safety zone)	3 (early warning zone)	5 (danger zone)	7 (high-risk zone)

Source: Based on the comprehensive judgment of “CFSI, FS-14, FAI.”