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

Table 3

Drivers’ self-ratings of workload, comfort, safety, and trust related to driving with the ACC on dry and snowy roads with various grip potentials ().

Subjective variable	Road condition and grip potential	Mean	Standard deviation	95% confidence interval
				Lower limit	Upper limit
Mental Demand	Dry ()	−2.85	0.22	−3.28	−2.42
	Snow ()	−2.46	0.25	−2.96	−1.96
Physical Demand	Dry ()	−3.33	0.20	−3.72	−2.94
	Snow ()	−3.07	0.22	−3.51	−2.64
Temporal Demand	Dry ()	−3.36	0.19	−3.74	−2.98
	Snow ()	−3.07	0.22	−3.49	−2.64
Performance	Dry ()	2.39	0.28	1.85	2.94
	Snow ()	2.23	0.26	1.72	2.75
Effort	Dry ()	−2.93	0.23	−3.39	−2.46
	Snow ()	−2.45	0.25	−2.94	−1.96
Frustration	Dry ()	−3.23	0.23	−3.69	−2.78
	Snow ()	−3.10	0.23	−3.55	−2.65
Comfort	Dry ()	4.88	0.11	4.67	5.09
	Snow ()	4.85	0.11	4.63	5.07
Safety	Dry ()	4.63	0.12	4.38	4.87
	Snow ()	4.47	0.13	4.21	4.73
Trust	Dry ()	4.51	0.13	4.25	4.76
	Snow ()	4.38	0.14	4.11	4.65

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