Table 5.

Risk estimates with one or more passengers, compared with solo driving, by driver gender for teenage or young drivers (Question 4)

Type of crash and study	Driver agea	Pass. agea,b	Measure	Male drivers with 1 or more pass. versus 0		Female drivers with 1 or more pass. versus 0		Male versus female drivers		Detail on type of crash
				Est.	95% CI	Est.	95% CI	Est.	95% CI
Fatal crashes
Chen et al., 2000	16–17	13–19	RR	1.63	1.54–1.74	1.43	1.31–1.55	1.15	1.03–1.28	Per 1,000 crashes
		13–191m		1.71	1.53–1.92	1.51	1.33–1.70	—	—
		13–192+m		1.99	1.74–2.26	2.40	1.98–2.89	—	—
		13–191f		.98	.87–1.11	1.29	1.15–1.45	—	—
		13–192+f		1.43	1.20–1.69	1.15	.99–1.33	—	—
		13–19fm		1.92	1.66–2.22	1.74	1.51–1.99	—	—
Doherty et al., 1998	16–19	Any	RRc	2.50	p < .10	3.55	p < .10	—	—	Per 100 million driver-km
	20–24			1.23	p > .10	1.75	p > .10	—	—
Geyer and Ragland, 2004	15–19	Any	AORd	.97	.93–1.03	.71	.66–.77	—	—	At fault versus not at fault
	20–24			1.13	1.07–1.19	.87	.80–.96	—	—
Ouimet et al., 2010	15–20	16–20	RR	5.55	5.16–5.98	4.09	3.63–4.61	1.36	1.18–1.56	Per 10 million VT
		16–20m		7.99	7.34–8.69	5.63	4.71–6.72
		16–20f		2.97	2.63–3.36	3.50	3.03–4.05
		16–20		6.26	5.81–6.74	4.24	3.76–4.77	1.48	1.28–1.70	Per 10 million VMT
		16–20m		9.94	9.13–10.81	4.06	3.40–4.85
		16–20f		3.29	2.91–3.72	4.36	3.78–5.04
Tefft et al., 2013	16–17	≤20	RR	1.85	1.66–2.07	1.52	1.31–1.76	1.22	1.01–1.46	Per 100 million miles driven
		≤201		1.67	1.12–2.50	1.16	.65–2.06
		≤202		1.84	1.08–3.12	2.28	1.35–3.86
		≤203+		3.57	.79–16.19	6.41	3.21–12.81
Nonfatal and combined fatal/nonfatal crashes
Doherty et al., 1998	16–19	Any	RRc	2.29	p < .10	1.91	p < .10	—	—	Injury; per million driver-km
	20–24			.70	p < .05	1.37	p > .10	—	—
	16–19			1.87	p < .10	1.58	p < .05	—	—	Material; per million driver-km
	20–24			.53	p < .10	1.12	p > .10	—	—
Engstrom et al., 2008	18–24	Any	RRe	.43	.41–.44	.30	.28–.32	1.40	1.31–1.51	Injury-fatal; per 10 million km
		Any1		.48	.46–.50	.36	.33–.38
		Any2		.40	.38–.44	.24	.21–.28
		Any3+		.28	.26–.31	.16	.13–.19
Orsi et al., 2013	≤24	Any	OR	1.88	1.31–2.69	1.29	.68–2.45	1.45	.93–2.27	Injury-fatal; with injury versus without injury
			AOR	—	—	—	—	—	—
Rueda-Domingo et al., 2004	18–24	16–24m	OR	1.15	1.08–1.23	.99	.84–1.17	—	—	Injury-fatal; at fault versus not at fault
		16–24f		.60	.56–.63	.86	.78–.96	—	—
		16–24m	AOR	.95	.87–1.04	.88	.70–1.11	—	—
		16–24f		.63	.58–.68	.94	.82–1.07
Tefft et al., 2013	16–17	≤201	RR	1.17	.72–1.90	1.05	.55–1.99	—	—	Police-reported; per one million miles driven
		≤202		1.04	.57–1.89	1.38	.78–2.44	—	—
		≤203+		1.70	.37–7.89	3.47	1.73–6.96	—	—

Estimates and CIs that were extracted from articles are not in italics; those that were calculated to answer the specific research questions are in italics. Estimates and CIs were only calculated when there were raw data addressing the specific research questions. Calculations might be affected by both rounding to a few decimals in source articles and adjustment based on sampling, which may results here in narrower intervals that should be interpreted with caution.

₊ =or more; ₁ =1 passenger; ₂ =2 passengers; ₃ =3 passengers; CI =confidence interval; AOR =adjusted odds ratio; Est. =Estimate; _f =female; _m =male; OR =odds ratio (or crude odds ratio); Pass. =passenger; RR =relative risk.

^aSections about driver and passenger age can also include details about gender and number of passenger if the data were only reported as such in articles.

^b“Any” describes studies including passengers of any age. When the information about passenger age was not provided, it was assumed that any passenger age was included.

^cThis study presented crash rates for male and female drivers separately. We calculated estimates, but significance was provided in the article.

^dEstimates and CIs for male and female drivers were extracted from figures in the article.

^eThis article compared solo driving versus passenger presence; so, estimates and CIs were extracted from the article, and scores were inverted to answer the current research question.