Drivers’ Interaction with Adaptive Cruise Control on Dry and Snowy Roads with Various Tire-Road Grip Potentials

Table 4

Drivers’ self-ratings of workload, comfort, safety, and trust related to driving with different time gaps of the ACC ().

Subjective variable	ACC GAP	Mean	SD	95% confidence interval
				Lower limit	Upper limit
Mental Demand	1 second	−2.48	0.23	−2.94	−2.03
	1.8 seconds	−2.82	0.23	−3.27	−2.38
Physical Demand	1 second	−3.16	0.21	−3.58	−2.75
	1.8 seconds	−3.25	0.20	−3.65	−2.85
Temporal Demand	1 second	−3.13	0.20	−3.52	−2.73
	1.8 seconds	−3.30	0.20	−3.70	−2.91
Performance	1 second	2.33	0.25	1.84	2.83
	1.8 seconds	2.29	0.28	1.74	2.84
Effort	1 second	−2.54	0.24	−3.01	−2.06
	1.8 seconds	−2.84	0.23	−3.30	−2.38
Frustration	1 second	−2.92	0.25	−3.42	−2.43
	1.8 seconds	−3.41	0.20	−3.81	−3.01
Comfort	1 second	4.64	0.12	4.40	4.88
	1.8 seconds	5.09	0.10	4.89	5.26
Safety	1 second	4.14	0.15	3.85	4.43
	1.8 seconds	4.95	0.12	4.72	5.18
Trust	1 second	4.17	0.15	3.87	4.46
	1.8 seconds	4.72	0.12	4.48	4.96

Note: ranges of the scales are specified in Section 2.4.