Table 2.

Group differences on the road test (RIRT) and naturalistic driving (CDAS).

	Healthy Controls (n= 44)	Patients (n=59)	t	p-value
Road Test Error Score mean (± SD)	0.04 (0.03)	0.08 (0.06)	−4.20	<0.001
Global Safety Rating (RIRT, %)
Pass (no recommendations)	56.82	20.34
Pass (with recommendations)	29.55	32.20
Marginal (with restrictions)	11.36	30.51
Marginal (with training)	2.27	15.25
Fail	0.00	1.69		<0.001
Naturalistic Driving Error Score mean (± SD)	0.10 (0.08)	0.19 (0.13)	−4.08	<0.001
Global Safety Rating (CDAS; %)
Pass (no restrictions)	61.36	35.59
Pass (with recommendations)	22.73	20.34
Marginal (with restrictions)	13.64	20.34
Marginal (with training)	2.27	16.95
Fail	0.00	6.78		0.01
Naturalistic Driving Course Difficulty mean (± SD)	5.80 (1.15)	5.68 (1.32)	0.47	0.64

RIRT = Rhode Island Road Test; CDAS = Composite Driving Assessment Scale.

Error scores reflect the average score on a 0-2 Likert scale (0=normal; 1-mildly impaired; 2-moderately-severely impaired.

Course difficulty was rated on a 10-point likert scale with 1=simple and 10=extremely challenging.