Table 1.

Sample size and weighted estimates of vehicle miles driven and vehicle hours driven by driver age category, gender, time-of-day, and day-of-week

	NHTS a			ATUS b
	Unweighted No. of trips	Weighted vehicle miles driven (95% CI c) (100 million miles)	Coefficient of variation e	Unweighted No. of trips	Weighted vehicle hours driven (95% CI d) (100 million hours)	Coefficient of variation
Age category
16–24	29,615	2,096 (1,925, 2,267)	0.04	1,680	89 (78, 99)	0.04
25–44	153,968	7,864 (6,933, 8,795)	0.06	10,422	282 (268, 296)	0.06
45–64	241,854	7,453 (7,169, 7,737)	0.02	10,022	285 (272, 298)	0.02
≥ 65	171,914	2,807 (2,621, 2,993)	0.03	5,206	111 (103, 118)	0.03
Gender
Female	299,943	8,710 (7,946, 9,475)	0.04	12,944	344 (329, 359)	0.02
Male	297,408	11,510 (11,029, 11,991)	0.02	14,389	422 (402, 443)	0.02
Time-of-day
Daytime	495,409	16,141 (15,312, 16,970)	0.03	21,407	590 (570, 609)	0.02
Nighttime	101,942	4,079 (3,854, 4,304)	0.03	5,923	176 (167, 186)	0.02
Day-of-week
Weekend	123,941	5,839 (5,581, 6,097)	0.02	12,613	223 (214, 232)	0.02
Weekday	473,410	14,381 (13,488, 15,275)	0.03	14,717	543 (521, 564)	0.02

^aNHTS: National Household Travel Survey;

^bATUS: American Time Use Survey;

^cThe confidence intervals (CIs) of the weighted estimates for vehicle miles driven on the national scale were obtained using the Jackknife approximation method;

^dThe confidence intervals (CIs) of the weighted estimates for vehicle hours driven on the national scale were obtained using the successive differences replication method;

^eCoefficient of variation is the ratio of the standard deviation to the mean.