Traffic Safety Facts 

Research Note 

September 2003 DOT HS 809 636 

Younger Drivers and Sport Utility Vehicles 

John Kindelberger and Ana María Eigen* 

In the years 1992 through 2001, 986 

sport utility vehicle (SUV) drivers of 

ages 16 through 19 years were fatally 

injured in U.S. rollover crashes – 128 in 

the year 2001, the most recent year for 

which complete data exist in the Fatality 

Analysis Reporting System (FARS). In 

these same years, 1,345 SUV drivers 

of ages 20-24 sustained fatal injuries 

in rollovers; of these, 326 occurred in 

the year 2001. Serious injuries were 

sustained in SUV rollovers by an 

estimated 16,000 drivers of ages 16-24 

in the years 1992-2001, as estimated 

by the National Automotive Sampling 

System’s General Estimates System 

(GES). 

In response to concerns over numbers 

such as those cited above, this note 

looks at driving risks associated with 

younger drivers in SUVs. In the United 

States, the number of SUVs in the 

fleet has more than doubled from 10 

million in 1995 to 21 million in 20011

. 

With this increase, interest in the rate 

and circumstances of SUV crashes 

(particularly rollovers) has grown. In 

particular, members of the safety 

community are concerned about the 

increase in use of aging SUVs by younger 

drivers who may lack experience in the 

handling of these vehicles, but may 

be buying the used vehicles as they 

become affordable. 

To address the concerns raised, this 

note addresses the following topics: 

■ Younger drivers in SUV crashes 

■	 Relative risk of rollover among 

differing age groups 

■ Rollovers in aging SUVs 

■ Groups at high risk 

For this note, drivers of ages 16 through 

24 are classified as younger drivers. 

Background 

Based on weighted estimates extracted 

from the GES, about 114 million 

drivers at least 16 years old were 

involved in police-reported crashes 

over the period 1992 through 2001. 

About 2.5 million of these crashed 

vehicles experienced a rollover, of 

which an estimated 1.6 million resulted 

in fatal or non-fatal injuries to either 

drivers or passengers. About 20 

percent of these vehicles were SUVs. 

Among all rollovers, about 40 percent 

occurred with a younger driver at the 

wheel, and about 36 percent of these 

younger drivers were in SUVs. 

As SUVs have grown in popularity, 

numbers of crashes involving SUVs 

have grown as well. Younger drivers 

have traditionally been involved in about 

25 percent of SUV crashes (Table 1). 

*John Kindelberger is a Mathematical Statistician and Ana María Eigen is a Mechanical Engineer with the 

Mathematical Analysis Division of the National Center for Statistics and Analysis, NHTSA. 

1

Source: R.L. Polk Co. 

Table 1 

Younger (16-24 yrs) Drivers in SUV Crashes 

Numbers and Proportions by Year 

Source: NCSA, NHTSA, NASS GES 1992-2001 

Definitions and Constraints 

The GES is a nationally representative 

weighted sample of police reported 

motor vehicle crashes of all types, from 

minor to fatal. This note’s analyses 

were conducted on GES cases from 

1992 through 2001 involving drivers 16 

years old in passenger cars, SUVs and 

non-SUV light trucks. SUV status was 

assigned to GES classified compact 

utility vehicles, large utility vehicles, and 

utility station wagons. For this note 

“non-SUV” light trucks include vans, 

minivans, and pickups. Excluded are 

buses, motorcycles, snowmobiles, 

motor homes, construction equipment, 

all-terrain vehicles, farm equipment, 

large limousines, or medium to heavy 

trucks. The GES body type variable 

categories have not changed since 

1992, so the years analyzed do not differ 

in that respect. 

Year Younger 

Drivers in 

SUV Crashes 

Younger Drivers 

as Proportion of 

All SUV Crashes 

1992 99,000 25% 

1993 113,000 27% 

1994 128,000 27% 

1995 133,000 27% 

1996 149,000 26% 

1997 151,000 25% 

1998 163,000 24% 

1999 235,000 23% 

2000 268,000 24% 

2001 321,000 27% 

National Center for Statistics and Analysis 400 Seventh St., S.W., Washington, D.C. 20590 
The data were segmented for analysis 

into the following variables: 

■ Driver age: Younger (16-24)/ older (25+) 

■ Vehicle type: SUV/non-SUV 

■ 	Vehicle crash type: Rollover/ 

non-rollover 

■ 	Vehicle age in years: Derived from 

model year (MY) and crash date 

■ Vehicle age category: Less than 

5 years/5 years or more 

■ Model year category: 1997 or 

earlier/1998 or later 

Driver gender was used as it appears 

in the GES. The question of chassis 

was not addressed and SUVs were 

examined in total because of the body 

type limitations in the GES. 

To test the significance of relative 

risks and odds ratios under the GES 

sample design, the SUDAAN (SUrvey 

DAta ANalysis Software for Statistical 

Analysis of Correlated Data) software 

package was utilized. 

Analyses 

Rollover Injuries 

In the GES data, given that a policereported crash has occurred where 

a passenger car or light truck has 

rolled over, the likelihood of at least 

one occupant in the rollover vehicle 

SUV Rollovers 

In the weighted GES data from 1992 

through 2001, given that a vehicle is 

involved in a police-reported crash, the 

estimated incidence of rollover (injury 

or not) for SUVs was a statistically 

significant 5.19 percent. This rate 

translates to an estimated 359,000 

SUV rollovers in the 10-year period. 

(Statistical significance in this note refers 

to a 95 percent confidence level.) 

The comparable rate for non-SUVs was 

2.00 percent. Thus, in the universe of 

GES-eligible police-reported crashes, 

the estimated risk of rollover for SUV 

drivers relative to that of non-SUV 

drivers is 5.19/2.00=2.59, or more than 

two and one half times as high. This 

number is called the “relative risk” and 

is statistically significant in this result. 

All age groups were more likely to roll 

over in an SUV than in a non-SUV, as 

summarized in Table 2. 

Table 2 

Rollover Percentages and Relative Risks 

By Vehicle Type and Driver Age Group 

Among Police Reported Crashes 1992-2001 

for younger drivers. The difference is not 

limited to SUVs among passenger cars 

and non-SUV light trucks, the GES data 

indicate that younger drivers are twice 

as likely to roll over in a crash than older 

drivers (Table 3). 

Table 3 

Rollover Percentages and Relative Risks 

By Vehicle Type and Driver Age Group 

Among Police Reported Crashes 1992-2001 

Source: NCSA, NHTSA, NASS GES 1992-2001 

Gender 

About 65 percent of younger drivers 

and 58 percent of older drivers in SUV 

crashes were male. Among younger 

SUV drivers, male drivers were found to 

be 23 percent more likely to roll over in 

a crash than female drivers. The gender 

difference for older drivers was not 

statistically significant (Table 4). 

Table 4 

Rollover Percentages and Relative Risks 

By Driver Age Group and Driver Gender 

Among Police Reported Crashes 1992-2001 

Rollover Percentage 

Relative 

Driver Gender Risk of 

Rollover, 

Driver Age Male vs. 

Group Female 

Male Female Driver 

16-24 6.46 1.23 

25 and up 4.66 4.10 Nonsignificant 

7.94 

Rollover Percentage 

Relative 

Risk of 

Rollover, 

Younger vs. 

Older Driver 

Vehicle 

Type 

Driver Age Group 

16-24 25 and up 

SUV 7.43 4.42 1.68 

Non-SUV 3.14 1.55 2.03 

suffering injury at any level

2

 is about 

63 percent. This proportion was not 

found to differ significantly across 

age groups. The analogous risk for 

incapacitating or fatal injury2, again 

across driver age groups, is about 18 

percent. Since injury probabilities were 

found to be similar across groups once 

a rollover has occurred, the rollover 

analyses of this note are conducted with 

the event of interest being any rollover 

– regardless of resulting injury level - to 

take advantage of the larger sample 

size. 

2

Injuries in the NASS GES are assessed by police 

officers on the observational KABCO scale 

where K=Killed; A=Incapacitating Injury; B=NonIncapacitating Injury; C=Possible Injury; O=No 

Injury; and U=Injured, severity unknown. For this 

note, “serious or fatal” refers to K or A on the 

KABCO scale. 

Rollover Percentage 

Relative 

Vehicle Type Risk of 

Rollover, 

Driver Age SUV vs. 

Group non-SUV 

SUV Non-SUV 

All 5.19 2.00 2.59 

16-24 7.43 3.14 2.36 

25 and up 4.42 1.55 2.86 

Source: NCSA, NHTSA, NASS GES 1992-2001 

Note that the relative risk does not 

depend on the relative proportions 

of SUV to non-SUV in the crash 

population, but rather on the proportions of rollovers in crashes within each 

vehicle type. 

Driver Age 

The highest individual rollover risk in 

Table 2 is that of drivers of ages 16-24 in 

SUVs, who experienced rollovers in 7.43 

percent of their crashes. The comparable 

percentage of older drivers was 4.4 

percent, so the relative risk is 7.4/4.4 = 

1.68, denoting a 68 percent higher risk 

Source: NCSA, NHTSA, NASS GES 1992-2001 

The gender difference is also seen in 

non-SUVs, where males across age 

groups were about 50 percent more 

likely to rollover in a crash. 

Rollovers in Aging SUVs 

To examine the possible consequence 

of older used SUVs becoming affordable for a new batch of (possibly 

National Center for Statistics and Analysis 400 Seventh St., S.W., Washington, D.C. 20590 
younger) owners, relative risk of rollover 

was assessed for both driver age 

groups in older vs. newer SUVs. In GES 

data, the risk of a young driver rollover 

in an older (5 or more years on crash 

day) SUV is 1.16 times that of a young 

driver rollover in a newer SUV, a risk 

increase of 16 percent. In older drivers, 

the risk increase is 23 percent. Thus, 

the risk of rollover has been higher in 

older SUVs than in newer ones for both 

age groups (Table 5). 

Table 5 

Rollover Percentages and Relative Risks 

By Driver Age Group and Vehicle Age 

Among Police Reported Crashes 1992-2001 

Rollover Percentage 

Relative 

Vehicle Age on Risk of 

Crash Date Rollover, 

Driver Age Male vs. 

Group Female 

5 Years Less than Driver 

or More 5 Years 

16-24 6.77 1.16 

25 and up 4.92 3.99 1.23 

7.85 

Source: NCSA, NHTSA, NASS GES 1992-2001 

The effect is not limited to SUVs. For 

GES passenger cars and non-SUV light 

trucks over all driver ages, rollover risk 

was found to be 23 percent higher in 

an older vehicle than in a newer one. 

The apparent vehicle age effect raises 

certain questions, such as: Is the 

observed difference an effect of the 

number of years the vehicle has been in 

use, or of design changes through the 

model years? To explore this question, 

a logistic regression model was fit 

where the population was SUVs in GES 

crashes, the response was rollover, and 

the predictors were driver age; driver 

sex; model year category (with cutoff 

year 1998); and vehicle age in years. 

Both types of vehicle age variables 

were included to allow a vehicle 

aging effect test while controlling for 

model year. The numerical rather than 

categorical setup for vehicle aging 

was necessary because in the 1998 

or newer model year category no 

vehicle was over 5 years old in 2001, 

and was desirable because logistic 

regression allows numerical variables 

as predictors, enabling a test for an 

incremental vehicle aging effect. 

Table 6 gives a brief explanation of 

each variable and its effect on the 

odds of a rollover (when all other 

model variables are held constant) as 

determined by the statistic known as 

the “odds ratio.” Note that the odds 

ratio is similar in form to the relative risk, 

but reflects the increase of the odds 

of the rollover, where the odds in this 

situation are defined as 

Probability of Rollover/ 

(1 – Probability of Rollover). 

Table 6 

Results of Logistic Regression 

Where Population is SUVs in Police-Reported 

Crashes (US 1992-2001) and Response is 

Rollover 

Odds Ratios and Explanations by Significant 

Variable 

Increase in Odds 

Variable Odds Ratio of Rollover 

Driver Age 1.63 63% increase 

Group if driver 16-24 

Driver 1.13 13% increase 

Gender if driver male 

Vehicle Age 1.03 3% increase 

in Years for each 

(1,2,3...) added year of 

vehicle age 

Model Year Not statistically significant 

(pre- or – dropped from model 

post- 1998) 

Source: NCSA, NHTSA, NASS GES 1992-2001 

As detailed in Table 6, the model year 

variable was not found to be statistically 

significant in this model, but the vehicle 

age-in-years effect is seen as a three 

percent increase in the odds of rollover 

for every added year of vehicle use. 

Although that odds ratio may seem 

small, it was statistically significant, and 

would “compound” over each additional 

year of age. 

For another look at this extended age 

effect, a similar model was run on MY 

1997 or earlier vehicles only but used 

the categorical vehicle age of “5 years 

or older” vs. “less than five years old.” 

In this model, the odds of rollover 

were 19 percent higher for the older 

vehicle category. 

The conclusion suggested by the 

preceding results is that, under 

conditions seen in the recent past, 

SUVs become more likely to be involved 

in rollovers as they age. It may be more 

reasonable to suggest that the age 

“effect” is in fact due to some other 

factor or factors related to vehicle age, 

such as driver socio-economic status or 

vehicle condition. For instance, younger 

SUV drivers (of both genders) have a 

greater tendency to be in older SUVs 

– 61 percent as compared to 46 percent 

of the older drivers. However, the driver 

age and vehicle age factors each 

supplied a significant main effect to the 

model, independently of each other. 

An interaction term was not significant; 

this simply means that the driver age 

effect and the vehicle age effect do not 

depend on each other. 

Although the premise of the vehicle age 

makes sense from a socio-economic 

standpoint, the engineering issues 

are less clear. Similar to other vehicle 

types, the SUV suffers the detriments 

of disrepair. Modifications in design 

uniquely act to improve SUV handling. 

As vehicles age, greater care must be 

given to brakes, tires, engine function, 

and transmission operation. These 

issues cannot be easily disaggregated 

from those that are inherent to handling 

of older vehicles. For example, within 

a GES qualified case, braking failures 

may exist with evidence remaining at 

the crash site, however, no recording 

mechanism exists to capture these 

data. Further, the state of tire repair 

may be masked by the events of 

the crash as in the case of tread 

separation. Engine or transmission 

malfunction, although speculative, also 

impair driving operations. 

Although the model year variable was 

not significant in the GES analysis, 

further research may be called for as 

National Center for Statistics and Analysis 400 Seventh St., S.W., Washington, D.C. 20590 
data accumulate. SUVs have undergone 

design changes over the period of this 

study, including but not limited to: 

suspension, steering, and changing tire 

requirements. The first generation of 

SUVs operated like their heavier truck 

counterparts. Steering inputs require 

great precision and penalty exists for 

exaggerated movements. SUVs do not 

benefit from the recovery characteristics 

inherent to passenger cars. In concert 

with the suspension changes are 

variation in the tires used for the SUV. In 

earlier SUVs, light truck tires enhanced 

the handling discrepancies with the 

passenger car. In the second generation 

of SUVs, however, passenger car tires 

have become more pervasive. 

When considering the effect of young 

drivers versus older drivers, it may be 

noted that inexperience likely acts to 

increase the risk of rollover crashes, but 

the effect of older vehicles complicates 

this issue. It may be useful to examine 

younger drivers operating older vehicles 

with regard to inexperience with SUV 

handling and mechanical difficulties. 

The disaggregating of these two 

conditions becomes very complicated 

with existing data. Within the data sets, 

it is possible to identify the model year 

of the vehicle and calculate the years it 

has been in service at the date of the 

crash, but the vehicle condition prior to 

the crash due to waning maintenance 

may be unknown and no clear method 

exists for uniform tracking. 

Limitations 

The risk and odds estimates in 

this analysis used only data from 

the GES, a weighted sample of 

all US police-reported crashes. 

This study was restricted to more 

general characteristics and does not 

address behavior-based variables such 

as alcohol, speeding, and safety belt 

usage. Further research is needed to 

explore the relationship between 

behavior-based variables and SUV 

rollover crashes among younger drivers. 

Conclusions 

Analysis of GES data for the years 

1992 through 2001 produced certain 

significant findings regarding drivers in 

SUV rollovers: 

■	 As a group, drivers of ages 16-24 

in crashes have been significantly 

more likely to roll over than drivers 

over age 24. 

■ 	Among younger drivers of SUVs that 

crashed, males have been more 

likely to roll over than females. The 

gender difference for older SUV 

drivers was negligible. 

■ 	In both younger and older drivers, 

older SUVs in crashes have been 

more likely to roll over than newer 

SUVs. 

■ 	Effects on rollover of driver age, 

driver gender, and vehicle age are 

not limited to SUVs, but the higher 

risk of rollover in an SUV crash adds 

to the overall risk where the other 

variables are involved. 

NHTSA plans to continue research into 

the subject of this note. Potential areas 

of further inquiry include behaviorbased variables in different age groups 

and vehicle types, the aging effect in 

various vehicle types, and application 

of exposure data from appropriate 

databases. NHTSA will continue to 

provide information on younger drivers, 

SUVs, rollovers and similar issues 

as data become available and new 

research is conducted. 

For additional copies of this research note, please call 1-800-934-8517 or fax your request 

to 202-366-3189. For questions regarding the data reported in this research, contact John 

Kindelberger (202-366-3365) or Ana María Eigen (202-366-2903). This research note and other 

general information on highway traffic safety may be accessed by internet users at: http://wwwnrd.nhtsa.dot.gov/departments/nrd-30/ncsa/AvailInf.html 

National Center for Statistics and Analysis 400 Seventh St., S.W., Washington, D.C. 20590