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ORIGINAL CONTRIBUTION
Elderly Licensure Laws
and Motor V ehicle Fatalities
David C. Grabowski, PhD
Christine M. Campbell, AB
Michael A. Morrisey, PhD
M
OTOR VEHICLE FATALITY
rates among older driv-
ers have been increasing
since 1980, particularly
among those aged 85 years or older.
1
Moreover, elderly individuals have more
fatal crashes per mile driven than any
other group except teenage males.
2
The
aging of the US population over the next
25 years makes these statistics particu-
larly distressing. According to the Insur-
ance Institute for Highway Safety: “Driv-
ers aged 65 and older...areexpected
to account for as much as 25 percent of
total driver fatalities in 2030, compared
to 14 percent currently.”
3
Although there
is debate among clinicians about the ap-
propriate role of public policy in regu-
lating older drivers,
4,5
the American
Medical Association recently released a
report calling on physicians to help older
motorists drive more safely by testing
motor skills and by regulating medica-
tions.
6
Growing public concern over this
issue is reflected in newspaper editori-
als calling for stricter licensure laws
among the elderly.
7-9
State governments have a variety of
methods for increasing the stringency
of the licensure process for elderly in-
dividuals, including the adoption of in-
person renewal requirements, vision
tests, road tests, and the implementa-
tion of a shorter renewal period. To our
knowledge, there is no study that ex-
amines the relationship of these 4 fea-
tures of licensure laws with elderly
driver fatalities using recent data.
10-12
Therefore, we conducted a retrospec-
tive, longitudinal study using recent
data of all fatal crashes in the contigu-
ous United States to provide a compre-
hensive examination of the relation-
ship between licensure laws and safety
among elderly drivers.
METHODS
Study Population
This study uses motor vehicle fatality
information from the 1990 through
2000 Fatality Analysis Reporting Sys-
tem (FARS). FARS, which is collected
by the National Highway Traffic Safety
Administration, is a census of all mo-
tor vehicle crashes on a trafficway cus-
Author Affiliations: Lister Hill Center for Health Policy
(Drs Grabowski and Morrisey and Ms Campbell), De-
partment of Health Care Organization and Policy (Drs
Grabowski and Morrisey), School of Public Health, Uni-
versity of Alabama, Birmingham (Drs Grabowski and
Morrisey and Ms Campbell).
Corresponding Author: David C. Grabowski, PhD, De-
partment of Health Care Organization and Policy,
RPHB 330, 1665 University Blvd, Birmingham, AL
35294 (grabowsk@uab.edu).
Context Little is known about how state-level driver licensure laws, such as in-
person renewal, vision tests, road tests, and the frequency of license renewal relate to
the older driver traffic fatality rate.
Objective To determine whether state driver’s license renewal policies are associ-
ated with the fatality rate among elderly drivers.
Design, Setting, and Population Retrospective, longitudinal study conducted Janu-
ary 1990 through December 2000 of all fatal crashes in the contiguous United States
identified in the Fatality Analysis Reporting System, which involved either an older (ages
65-74 years, 75-84 years, and ⱖ85 years) or middle-aged (ages 25-64 years) driver.
Two regression approaches were used to study the effect of state laws mandating in-
person renewal, vision tests, road tests, and frequency of license renewal on driver
fatalities, controlling for state-level factors including the number of licensed elderly
drivers, primary and secondary seatbelt laws, maximum speed limit laws, blood alco-
hol level of 0.08, and administrative license revocation drinking and driving laws, per
capita income, and unemployment rate. The first regression approach examined only
elderly driver fatalities and the second approach examined daytime elderly driver fa-
talities and used daytime fatalities among middle-aged drivers as a general control for
unobserved variation across states and over time.
Main Outcome Measures Older driver fatalities and older and middle-aged day-
time driver fatalities.
Results Among individuals aged 85 years or older, there were a total of 4605 driver
fatalities and 4179 daytime driver fatalities during the study period. For this age cohort,
after controlling for middle-aged daytime driver deaths, states with in-person license re-
newal were associated with a lower driver fatality rate (incident rate ratio [RR], 0.83; 95%
confidence interval [CI], 0.72-0.96). This was the only policy related to older drivers that
was significantly associated with a lower fatality risk across both regression models. Thus,
state-mandated vision tests, road tests, more frequent license renewal, and in-person re-
newal (for individuals aged 65-74 years and 75-84 years) were not found to be inde-
pendently associated with the fatality rate among older drivers in the 2 models.
Conclusions In-person license renewal was related to a significantly lower fatality
rate among the oldest old drivers. More stringent state licensure policies such as vi-
sion tests, road tests, and more frequent license renewal cycles were not indepen-
dently associated with additional benefits.
JAMA. 2004;291:2840-2846 www.jama.com
2840 JAMA, June 16, 2004—Vol 291, No. 23 (Reprinted) ©2004 American Medical Association. All rights reserved.
tomarily open to the public that re-
sulted in the death of a person within
30 days of the crash.
13
FARS contains
detailed information on the vehicles,
drivers, occupants, and nonoccupants
involved in the crash. We construct age,
state, and year-specific fatality counts
from FARS. The 11 years of FARS data
encompass a total of 74428 driver fa-
talities among individuals aged 65 years
or older within the contiguous United
States, excluding Washington, DC.
However, to ascertain the effects of cer-
tain motor vehicle licensure laws on
older drivers, we also include a com-
parison group of all fatal crashes in-
volving drivers aged 25 to 64 years.
There were 231488 fatalities for this co-
hort during the study period. State-
year is the unit of analysis; there were
528 observations (48 states⫻ 11 years)
in the complete dataset.
Data on motor vehicle laws and their
dates of enactment were obtained from
several sources. We began with com-
pilations of laws from the Insurance In-
stitute for Highway Safety.
14
We then
conducted a telephone survey of all state
departments of motor vehicles to con-
firm the laws, resolve inconsistencies,
and obtain the dates of changes in the
laws. In several instances, we used codes
of annotated state statutes and spe-
cific legislative acts available on the In-
ternet to determine when laws were
implemented.
Annual state unemployment rate data
and information on the consumer price
index were obtained from the US Bu-
reau of Labor Statistics.
15,16
Annual per
capita income data were collected from
the US Bureau of Economic Analysis
and adjusted for inflation using the con-
sumer price index.
17
Data on the num-
ber of licensed drivers by age group,
state, and year were collected by the
Federal Highway Administration and
compiled in multiple editions of High-
way Statistics.
18
Study Variables
The number of overall and daytime (7
AM to 7 PM) driver fatalities were com-
puted by age cohort for each year in each
state. Separate computations were made
for drivers aged 25 to 64 years, 65 to 74
years, 75 to 84 years, and 85 years or
older.
Both the specific licensing require-
ments and the length of the renewal pe-
riod may be related to older driver
safety. The first binary variable mea-
sures whether a state has in-person re-
newal. In 2000, 45 states were in this
category. The other 2 binary licensure
variables measure whether the state
used vision or road tests at the time of
license renewal. In 2000, 40 states re-
quired vision testing for older drivers
renewing their licenses and 2 states re-
quired road tests. Importantly, the in-
person renewal, vision, and road tests
are not mutually exclusive categories.
Each binary variable captures the in-
dependent effect of the particular policy
on the traffic fatality rate holding the
other 2 policies constant. These laws are
expected to have meaningful effects in
reducing fatalities among older driv-
ers because they either demonstrate im-
paired driving ability, as in the case of
vision and road tests, or they provide
an opportunity for the license exam-
iner to observe potentially impaired
drivers, as in the case of in-person re-
newals. Since 1990, there has been only
minimal change in these laws within
states over time.
The frequency of the driver’s li-
cense renewal cycle was measured in
years; the average renewal cycle in 2000
was 4.35 years. Two states have short-
ened the period of renewal for older
drivers since 1990 and 3 states have
lengthened the renewal period for
younger drivers, but not for older driv-
ers. In 2000, 36 of the 48 contiguous
states used the same renewal provi-
sions for middle-aged and elderly driv-
ers and 14 states lengthened the re-
newal period for all adult drivers
between 1990 and 2000. A longer pe-
riod between license renewals is ex-
pected to increase fatalities. The longer
interval is hypothesized to reduce the
opportunity for license officials to ob-
serve the physical and mental condi-
tion of older license applicants whose
abilities may rapidly decline over time.
Additionally, a more frequent interval
may discourage some older drivers from
attempting to renew their license.
There are 6 other motor vehicle
laws that may affect fatalities among
older drivers that we include as covar-
iates in the model, which are mea-
sured as state-year specific dichoto-
mous variables.
10,19-21
First, primary enforcement of man-
datory seatbelt laws allows the police
to stop vehicles solely for belt-law vio-
lations; 16 states had such laws in 2000.
Second, secondary enforcement of seat-
belt laws allows police to issue a ticket
for a seatbelt violation, but only if there
was another infraction; by 2000, 31
states had enacted such laws. Third,
states have had the option to increase
the maximum speed limit to 65 mph on
rural interstate highways since 1987. In
1995, Congress repealed federal legis-
lation limiting speed limits. In 2000, 19
states had a rural speed limit of 65 mph
on rural interstates. Fourth, 29 states
had a rural speed limit of 70 mph or
higher on rural interstates in 2000.
Fifth, by 1988, all states except Mas-
sachusetts had per se laws that made
it a crime to drive with a blood alco-
hol level above 0.10. Between 1988 and
2000, 14 states lowered the legal thresh-
old from 0.10 to 0.08. In 2000, Con-
gress made the lower level the na-
tional standard. Sixth, in 2000, 39 states
had administrative license suspension
in which a driver’s license may be taken
before a conviction if a driver’s blood
alcohol level exceeds 0.08 or if the
driver refuses to take the test.
Earlier studies of motor vehicle fa-
talities report the importance of con-
trolling for the state of the economy.
22,23
Thus, the inflation-adjusted mean per
capita income and the unemployment
rate are included for each state-year
observation.
The number of licensed drivers was
reported by state and year for each of
the age cohorts. For the period 1990
through 1993, there were 40 missing
state-year observations for the cohort
aged 75 to 84 years and 69 missing
observations for the cohort aged 85
years or older. This variable was the
only source of missing data in this
MOTOR VEHICLE FATALITIES AMONG THE ELDERLY
©2004 American Medical Association. All rights reserved. (Reprinted) JAMA, June 16, 2004—Vol 291, No. 23 2841
study. The natural log of age-specific
licensed drivers is included as a mea-
sure of exposure in the multivariate
model. T
ABLE 1 reports the means
and SDs of the variables used in our
analysis for 2000. T
ABLE 2 summa-
rizes the number of state-year obser-
vations for which the various state
laws were applicable to older drivers
during the study period.
Of a total of 528 state-years in the data
set, in-person renewal was in effect for
495 state-years, vision tests were in effect
for 440 state-years, and road tests were
in effect for 22 state-years. The 65 mph
speed limit was in effect for 344 state-
years; 70 mph or higher speed limit, 131
state-years; primary enforcement of seat-
belt laws, 122 state-years; secondary en-
forcement of seatbelt laws, 357 state-
years; blood alcohol level of 0.08, 111
state-years; and administrative license re-
vocation, 371 state-years.
Statistical Analysis
The relationship of licensure laws and
fatalities was examined using 2 sepa-
rate estimation strategies. First, the
effect of licensure laws on the number
of elderly driver fatalities for the 3 older
age cohorts (65-74 years, 75-84 years,
ⱖ85 years) was examined in a multi-
variate regression framework, control-
ling for the other state laws, macroeco-
nomic factors, and the number of
age-specific licensed drivers.
The second estimation strategy rec-
ognizes that these other covariates
included in the first multivariate speci-
fication may not adequately control for
unobserved state-level factors that may
be correlated with both elderly licen-
sure laws and traffic fatalities. For
instance, the degree of state law enforce-
ment may be correlated with both the
stringency of elderly licensure laws and
the number of traffic fatalities. Thus, we
use an alternate specification that relies
on comparing the gap in fatalities
between older and middle-aged driv-
ers in states with and without these laws.
This approach has been used in other
contexts including the labor market
effects of mandated maternity benefits
and the effects of the minimum legal
drinking age on teen childbearing.
24,25
The model assumes that middle-aged
drivers should be subject to the same
unobserved state-specific factors as
older drivers (eg, the presence of law
enforcement), but road tests, vision
tests, in-person renewal, and the
renewal frequency are predominantly
important for the safety of the older age
cohorts because of the frequency of
detecting impairment is likely to be
small for the middle-aged cohort.
Because the majority of driver fatalities
among older adults occur during day-
light hours, we restrict the model to
fatalities among older and middle-aged
adults that occur between the hours of
7
AM and 7 PM. Thus, by comparing the
differential effect of these laws on older
relative to middle-aged daytime drivers
in the state, we account for unobserved
state-level factors in estimating the rela-
tionship between licensure laws and
driver safety among the elderly.
Table 1. State-Level Descriptive Statistics for 2000 (N = 48)
Statistic Value
Motor vehicle fatalities by age of driver, mean (SD)
Total
25-64 y 315.23 (285.06)
65-74 y 36.38 (32.81)
75-84 y 34.60 (30.24)
ⱖ85 y 11.90 (11.39)
Daytime
25-64 y 149.33 (128.27)
65-74 y 27.98 (24.24)
75-84 y 28.90 (25.44)
ⱖ85 y 10.65 (10.32)
Licensed drivers by age, median (25%-75%)
25-64 y 1 997 700 (900 617-3 460 082)
65-74 y 235 067 (106 565-362 750)
75-84 y 136 552 (55 270-203 484)
ⱖ85 y 30 896 (14 538-52 401)
Elderly licensure laws
In-person renewal, No. (%) 45 (0.94)
Vision test, No. (%) 40 (0.83)
Road test, No. (%) 2 (0.04)
Renewal period, mean (SD), y 4.35 (1.06)
Other state laws, No. (%) of states
Speed limit, mph
65 19 (0.40)
ⱖ70 29 (0.60)
Seatbelt
Primary 16 (0.33)
Secondary 31 (0.65)
Blood alcohol level of 0.08 16 (0.33)
Administrative license suspension 39 (0.81)
Other, mean (SD)
Per capita income $16 226 ($2599)
Unemployment rate 3.84 (0.88)
Table 2. Number of State-Years That Policy
in Effect (1990-2000)
Law
No. of
State-Years
In-person renewal 495
Vision test 440
Road test 22
Speed limit, mph
65 344
ⱖ70 131
Seatbelt
Primary 122
Secondary 357
Blood alcohol level of 0.08 111
Administrative license
suspension
371
Total
*
528
*
Total number of annual state-year observations for which
a policy was applicable to older drivers. The total sample
includes 11 annual observations for each of the 48 con-
tiguous states included in the study.
MOTOR VEHICLE FATALITIES AMONG THE ELDERLY
2842 JAMA, June 16, 2004—Vol 291, No. 23 (Reprinted) ©2004 American Medical Association. All rights reserved.
We implement this strategy by in-
cluding state-year observations repre-
senting both older and middle-aged
driver fatalities (ages 25-64 years)
within the regression model. Thus, the
complete data set includes 1056 obser-
vations (ie, 11 years⫻ 48 states ⫻ 2 age
groups). The statistical test is accom-
plished by interacting the 4 state laws
with age-cohort dichotomous vari-
ables. It is the interaction of older age
and the presence of one of these laws
that measures the estimated addi-
tional impact on older drivers relative
to middle-aged ones.
It should be noted that this approach
assumes that the same factors influ-
ence daytime traffic fatality rates among
both middle-aged and older adults in a
given state and year. The first specifica-
tion, which includes state-year obser-
vations from the elderly age cohorts only
may actually be preferable. There is little
basis for distinguishing the approaches
a priori. Therefore, the models are best
viewed as complementary approaches
for exploring the validity of this study’s
key findings.
To account for zero values in some
state-year traffic fatality observations for
the older age categories, all the equa-
tions are estimated as count models us-
ing negative binomial models. We used
STATA regression statistical software
(version 8.0, STATA Corp, College Sta-
tion, Tex). Because of the likely pres-
ence of heteroskedasticity in the
grouped state-year data, the Huber-
White estimator was used to obtain ro-
bust SEs.
26
RESULTS
T
ABLE 3 contains results from the first
multivariate specification examining the
relationship of licensure laws and the
elderly driver fatality rate. In this model,
only 2 statistically significant findings
emerge across the 3 age cohorts. First,
those states with a law mandating in-
person renewal were associated with a
lower fatality rate for drivers aged 85
years or older relative to states with-
out in-person renewal (incident rate ra-
tio [RR], 0.83; 95% confidence inter-
val [CI], 0.71-0.96). During the study
period, there were 4605 total driver fa-
talities within this age cohort. Second,
those states with vision tests laws were
associated with a lower (incident RR,
0.92; 95% CI, 0.85-0.99) fatality rate for
drivers aged 65 to 74 years relative to
states without vision test laws. During
the study period, there were 19688 total
driver deaths within this age cohort.
Road test laws and the state-mandated
length of the renewal period were not
independently associated with fatali-
ties in any of the 3 age cohorts.
T
ABLE 4 contains results from the sec-
ond multivariate specification, which ac-
counts for omitted variables by exploit-
ing variation in daytime fatality rates
among middle-aged drivers across states.
Once again, a state law mandating in-
person renewal was associated with a
lower driver fatality rate for those aged
85 years or older compared with those
aged 25 to 64 years (incident RR, 0.83;
95% CI, 0.72-0.96). This result is based
on 4179 daytime driver deaths within
this age cohort. However, a state law
mandating in-person renewal was not
significantly associated with the fatal-
ity rate for the 2 other age cohorts. State
laws pertaining to vision tests, road tests,
and the length of the renewal period
were not statistically associated with the
fatality rate among older drivers for any
of the 3 age cohorts.
COMMENT
This study represents the first compre-
hensive analysis of licensure laws and
the fatality rate among older drivers us-
ing recent national data. Across 2 al-
ternative multivariate specifications,
states with in-person license renewal
were found to be associated with a lower
driver fatality rate for the cohort aged
85 years or older. The estimates from
the 2 model specifications were remark-
ably similar. That is, the relative inci-
dence rate for states with in-person li-
cense renewal was roughly 17% lower
than those states with no in-person re-
newal. However, in-person renewal was
not associated with a lower fatality rate
among the 2 relatively younger co-
horts. Moreover, taken together, our 2
alternative estimation strategies indi-
cated that state laws mandating vision
tests, road tests, and more frequent re-
newals were not associated with a lower
Table 3. Association of Licensure Laws With Older Adult Driver Fatalities
Total No. of Deaths
Among Older Drivers
Adjusted
Incident RR (95% CI)
*
States
With Law
States
Without Law
Age 65-74 y (528 state-years)
In-person renewal 18 186 1502 1.05 (0.95-1.16)
Vision test 16 454 3234 0.92 (0.85-0.99)
Road tests 720 18 968 1.09 (0.97-1.21)
Renewal period, y† NA NA 1.01 (0.99-1.03)
Age 75-84 y (488 state-years)
In-person renewal 15 000 1297 0.95 (0.86-1.05)
Vision test 13 678 2619 0.95 (0.87-1.04)
Road tests 621 15 676 0.98 (0.87-1.12)
Renewal period, y† NA NA 1.01 (0.98-1.03)
Age ⱖ85 y (459 state-years)
In-person renewal 4275 330 0.83 (0.71-0.96)
Vision test 3911 694 1.07 (0.95-1.20)
Road tests 142 4463 1.01 (0.79-1.28)
Renewal period, y† NA NA 1.02 (0.99-1.05)
Abbreviations: CI, confidence interval; NA, not applicable; RR, rate ratio.
*
Adjusted for the natural log of licensed drivers in the given age cohort, the state unemployment rate, the real per
capita state income, and binary indicators for primary seatbelt, secondary seatbelt, 65 mph rural speed limit, 70 mph
or higher rural speed limit, blood alcohol level of 0.08, and administrative license suspension laws, and year dummy
variables. Models are estimated using negative binomial regression. Each regression includes state and year cells
representing the older age group (65-74 years, 75-84 years, or ⱖ85 years). The dependent variable is the count of
fatalities in the given age group. The CI was constructed using Huber-White adjusted SEs.
†Based on the increment of 1 year.
MOTOR VEHICLE FATALITIES AMONG THE ELDERLY
©2004 American Medical Association. All rights reserved. (Reprinted) JAMA, June 16, 2004—Vol 291, No. 23 2843
fatality rate among older drivers. Thus,
the bottom line from this study is that
in-person renewal is associated with a
lower fatality rate among the oldest old
drivers, but vision tests, road tests, and
more frequent renewals are not inde-
pendently associated with additional
safety benefits.
This study cannot address the exact
mechanism by which in-person license
renewal is related to the fatality rate
among elderly drivers (aged ⱖ85 years),
but we can speculate on 2 causal path-
ways. Both hypotheses stem from pre-
vious research that has found that states
with more stringent license renewal re-
quirements are associated with lower
rates of licensed elderly drivers.
27
First,
in-person renewal requirements pro-
vide an opportunity for license inspec-
tors to either refuse to grant licenses to
obviously impaired drivers or to refer
such persons for medical evaluation
prior to receiving a new license. Thus,
it may be the case that greater numbers
of potentially unsafe older drivers are de-
tected and refused a license within the
in-person renewal process.
Given this explanation, one may ex-
pect state laws mandating vision and
road tests to be associated with addi-
tional safety gains independent of in-
person license renewal, but our find-
ings did not support such a relationship.
Recent research has argued that vision
acuity is only weakly related to crash
involvement.
28
Thus, the vision acuity
tests used by most states in the license
renewal process may not detect addi-
tional unsafe drivers relative to in-
person renewal without such a vision
test requirement. However, it is impor-
tant to note that in-person renewal al-
lows driver license examiners the op-
portunity to refer certain older drivers
for medical evaluation, and some of
these evaluations may include more so-
phisticated testing such as neurologi-
cal examinations, comprehensive vi-
sual examinations, simulator tests, and
road tests. Thus, it would be a mistake
to conclude based on our results that
there is never a benefit to a compre-
hensive medical evaluation. On an in-
dividual basis, these evaluations may be
important toward identifying poten-
tially unsafe drivers. However, our in-
terpretation of the findings is that in-
person license renewal effectively
captures the “going to the department
of motor vehicles” phenomenon and
that state laws mandating vision and
road tests for all older drivers do not
offer independent benefits toward low-
ering the fatal crash rate among older
drivers.
A second hypothesis consistent with
our findings is that potentially unsafe
older drivers may be less likely to re-
apply for a license when facing in-
person renewal. That is, potentially un-
safe older adults may recognize the low
likelihood of relicensure and forego the
license renewal process altogether. Un-
fortunately, state-level data on the num-
ber of elderly applicants for licenses are
not available nationally over time, but
this explanation would fit into the
broader literature showing that older
drivers impose many restrictions on
their own driving behavior. For ex-
ample, older drivers have been found
to limit driving at night, in poor
weather, on highways, during rush
hour, and following at-fault crashes.
29
Moreover, other research has shown
that older adults limit their driving with
early changes in their spatial vision
function and depth perception.
30
In the
broad continuum of driving behav-
iors, the self-restriction of driving may
culminate in the cessation of driving al-
together. Although we cannot test this
relationship directly with our current
data, an in-person license renewal re-
quirement may serve as a deterrent to
relicensure for potentially unsafe el-
derly drivers.
Our findings differ in some respects
from the earlier literature on licensure
laws and older driver fatalities. In con-
trast to our findings, the existing lit-
erature has generally argued that vi-
sion tests are associated with lower
elderly driver fatality rates. In a multi-
variate study of the national FARS data
for the 5-year period (1985-1989) di-
rectly preceding our study period, Levy
et al
2
found that state-mandated tests
of visual acuity were associated with a
lower fatal crash risk for elderly driv-
Table 4. Association of Licensure Laws With Daytime Driver Fatalities
Total Older Driver
Daytime Deaths
Adjusted
Incident RR (95% CI)
*
States
With Law
States
Without Law
Age 65-74 y (1056 state-years)
In-person renewal 13 995 1157 1.06 (0.96-1.16)
Vision tests 12 661 2491 0.94 (0.87-1.02)
Road tests 540 14 612 1.08 (0.96-1.22)
Renewal period, y† NA NA 1.00 (0.98-1.03)
Age 75-84 y (976 state-years)
In-person renewal 12 767 1126 0.93 (0.84-1.02)
Vision tests 11 636 2257 0.98 (0.89-1.07)
Road tests 545 13 348 1.13 (1.00-1.27)
Renewal period, y† NA NA 1.00 (0.98-1.03)
Age ⱖ85 y (918 state-years)
In-person renewal 3869 310 0.83 (0.72-0.96)
Vision tests 3535 644 1.07 (0.94-1.21)
Road tests 127 4052 1.10 (0.87-1.40)
Renewal period, y† NA NA 1.02 (0.98-1.05)
Abbreviations: CI, confidence interval; NA, not applicable; RR, rate ratio.
*
Adjusted for the natural log of licensed drivers in the given age cohort, the state unemployment rate, the real per
capita state income, and binary indicators for primary seatbelt, secondary seatbelt, 65 mph rural speed limit, 70 mph
or higher rural speed limit, blood alcohol level of 0.08, and administrative license suspension laws, and year and age
cohort dummy variables. Models are estimated using negative binomial regression. Each regression includes state
and year cells representing both a middle-aged (25-64 years) and older age group (65-74 years, 75-84 years, or
ⱖ85 years). The dependent variable is the count of fatalities in the given age group. The CI was constructed using
Huber-White adjusted SEs.
†Based on the increment of 1 year.
MOTOR VEHICLE FATALITIES AMONG THE ELDERLY
2844 JAMA, June 16, 2004—Vol 291, No. 23 (Reprinted) ©2004 American Medical Association. All rights reserved.
ers aged 70 years or older. In a multi-
variate study of FARS data for the pe-
riod 1989 through 1991, Shipp
12
found
that vision test laws were significantly
associated with lower vehicle occu-
pant fatality rates among drivers aged
60 years or older. Finally, in a bivari-
ate study of FARS data from 20 states
for the period 1986 through 1988, Nel-
son et al
31
found that states with vi-
sion test laws were associated with a
lower fatal crash involvement rate for
drivers aged 65 years or older.
There are several explanations for the
different conclusions regarding vision
tests between our study and previous
work. First, we have specified our
model differently from earlier work by
separately examining the effects of in-
person license renewal and vision test
laws. The previous studies of vision test
laws have neglected to account for in-
person renewal by grouping all states
without vision test laws together in the
control group, regardless of whether the
state had in-person license renewal or
not. In 2000 for example, 5 states had
in-person renewal requirements with-
out mandating vision tests. Thus, the
negative association we observe be-
tween in-person renewal and the driver
fatality rate among the elderly in our
study may have been misattributed to
vision test laws in earlier studies.
Our multivariate estimates also dif-
fer from the earlier literature in several
other significant ways. Our data are more
recent (1990-2000) than the other stud-
ies. Other investigators generally exam-
ined data from the 1980s and early 1990s.
Given the trends toward increased licen-
sure rates and higher annual mileage
driven among older persons,
3
the ear-
lier data may be less relevant for today’s
elderly driving population. The inves-
tigators in earlier studies also did not con-
trol for state traffic laws unrelated to
licensure such as seatbelt, speed limit,
and alcohol-control laws. Our study is
the also first to recognize potential het-
erogeneity in the response to licensure
laws in the younger old and the older
old. Earlier work, which grouped all
elderly above a particular age together,
might have masked or distorted rela-
tionships within different elderly age
groups. For example, we found a statis-
tically significant relationship between
in-person license renewal and the elderly
driver fatality rate for the cohort aged 85
years or older, but no significant rela-
tionship among the cohort aged 65 to
74 years or the cohort aged 75 to 84
years.
A final distinction between this ar-
ticle and the earlier literature is the use
of the middle-aged daytime driver fa-
tality rate as a control for unobserved
variation in driving conditions across
states and over time. Because it is dif-
ficult to construct a fully specified
model due to data limitations, omit-
ted variable bias is always a concern
when modeling state motor vehicle
rates. Only 1 previous study in the lit-
erature explored a similar model speci-
fication as a (unreported) sensitivity
check to their main results.
2
Impor-
tantly, our main results remained es-
sentially stable when we introduced
middle-aged daytime drivers as a gen-
eral control within the model. This sen-
sitivity check supports the idea that un-
observed heterogeneity is not the
underlying source of our findings.
In regard to road test laws, previous
research generally supports our cur-
rent finding that these laws are not in-
dependently associated with lower fa-
tality rates among older adults. Levy et
al
2
found no significant association be-
tween road test laws and the driver fa-
tality rate among older adults. Simi-
larly, Rock
11
found that eliminating a
state law mandating road tests in Illi-
nois for drivers aged 69 to 74 years in
late 1989 did not increase the fatality
crash rate among elderly Illinois driv-
ers in this age group relative to a con-
trol group that experienced no change
in requirements. However, in contrast
to our findings, increasing the fre-
quency of renewal from 4 years to 2
years for those aged 81 to 86 years and
1 year for those aged 87 years or older
was found to significantly decrease the
fatality crash rate relative to the con-
trol group. One explanation for the dif-
ference in findings relative to our study
is that Illinois is one of the most strin-
gent states in terms of the frequency of
license renewal. By comparison, only
11% of the state-year observations in
our study had a renewal period of less
than 4 years. For those older drivers
with rapidly declining driving skills,
more frequent renewals may be neces-
sary to observe a significant decrease in
the fatality rate. Further work exam-
ining this issue is necessary.
The current study has limitations.
Some of the laws evaluated in this study,
such as road tests, have only been
implemented in a handful of states. This
makes it difficult to obtain precise es-
timates of their relationship with older
driver safety. In addition, little is known
about the degree of enforcement of the
license renewal tests across states and
over time. Moreover, we broadly clas-
sified states with and without vision test
laws without considering the level of
visual acuity required by states. In terms
of the FARS data, we can only mea-
sure the year of the fatal crash, not the
year in which the driver involved re-
newed his/her license. Although there
were few changes in state licensure laws
during our study, any changes during
the study (or in the years immediately
preceding the study) may have led us
to misclassify the state licensure laws
in effect at the time of license renewal.
Finally, FARS data only allow an in-
vestigation of fatalities; research also is
needed on the nonfatal consequences
of licensure laws for older drivers.
Across 2 different estimation strate-
gies, the results of this study support the
importance of in-person license re-
newal for older adults as a potential
mechanism toward decreasing the fa-
tality crash rate among the oldest old
drivers. However, more stringent state
licensure laws mandating vision tests,
road tests, and shorter renewal cycles
were not independently associated with
a decrease in the older driver fatality rate.
Author Contributions: Dr Grabowski had full access
to all of the data in the study and takes responsibility
for the integrity of the data and the accuracy of the
data analysis.
Study concept and design: Grabowski, Morrisey.
Acquisition of data: Grabowski, Morrisey.
Analysis and interpretation of data: Grabowski,
Campbell, Morrisey.
Drafting of the manuscript: Grabowski, Morrisey.
MOTOR VEHICLE FATALITIES AMONG THE ELDERLY
©2004 American Medical Association. All rights reserved. (Reprinted) JAMA, June 16, 2004—Vol 291, No. 23 2845
Critical revision of the manuscript for important in-
tellectual content: Grabowski, Campbell, Morrisey.
Statistical expertise:Grabowski, Morrisey.
Obtained funding: Grabowski, Morrisey.
Administrative, technical, or material support:
Campbell.
Supervision: Morrisey.
Funding/Support: This research was supported in part
by grant 01230 from the University Transportation
Center for Alabama and by grant R49/CCR403641
from the Centers for Disease Control and Preven-
tion, National Center for Injury Prevention and Con-
trol to the Injury Control Research Center at the Uni-
versity of Alabama at Birmingham.
Role of the Sponsor: Other than providing financial
support, the University Transportation Center for Ala-
bama and the Injury Control Research Center at the
University of Alabama, Birmingham, played no part
in the collection or analysis of these data or approval
of publication.
REFERENCES
1. Traffic Safety Facts 1999. Washington, DC: Dept
of Transportation, National Highway Safety Admin-
istration; 2000.
2. Levy DT, Wernick JS, Howard KA. Relationship be-
tween driver’s license renewal policies and fatal crashes
involving drivers 70 years or older. JAMA. 1995;274:
1026-1030.
3. Lyman S, Ferguson SA, Braver ER, Williams AF.
Older driver involvement in police reported crashes
and fatal crashes: trends and projections. Inj Prev. 2002;
8:116-120.
4. Fain MJ. Should older drivers have to prove that
they are able to drive? Arch Intern Med. 2003;163:
2126-2128.
5. Fitten LJ. Driver screening for older adults. Arch In-
tern Med. 2003;163:2129-2131.
6. American Medical Association Council on Scien-
tific Affairs. Older Driver Safety. Chicago, Ill: Ameri-
can Medical Association; 2003.
7. Screen older drivers better. USA Today. July 18,
2003. Available at: http://www.usatoday.com/news
/opinion/editorials/2003-07-17-edit_x.htm. Acces-
sibility verified May 18, 2004.
8. Elders behind the wheel. New York Times. July 27,
2003;§4:12.
9. Elderly drivers: road tests become more important
with age. Dallas Morning News. July 28, 2003;12A.
10. Grabowski DC, Morrisey MA. The effect of state
regulations on motor vehicle fatalities for younger and
older drivers: a review and analysis. Milbank Q. 2001;
79:517-545.
11. Rock SM. Impact from changes in Illinois drivers
license renewal requirements for older drivers. Accid
Anal Prev. 1998;30:69-74.
12. Shipp MD. Potential human and economic cost-
savings attributable to vision testing policies for driver
license renewal, 1989-1991. Optom Vis Sci. 1998;
75:103-118.
13. Fatality Analysis Reporting System. Department
of Transportation, National Highway Safety Admin-
istration Web site. Available at: http://www-fars.nhtsa
.dot.gov/. Accessibility verified May 18, 2004.
14. State laws—2002. Insurance Institute for High-
way Safety Web site. Available at: http://www
.hwysafety.org/safety_facts/safety.htm. Accessibil-
ity verified May 14, 2004.
15. Consumer price index, all urban consumers—
2003. Bureau of Labor Statistics Web site. Available
at: http://data.bls.gov/cgi-bin/surveymost?cu. Ac-
cessibility verified May 18, 2004.
16. Historical state labor force data—2002. Bureau of
Labor Statistics Web site. Available at: http://www.bls
.gov/lau/home.htm. Accessibility verified May 14, 2004.
17. Annual state personal income—2002. Bureau of
Economic Analysis Web site. Available at: http://www
.bea.gov/bea/regional/data.htm. Accessibility veri-
fied May 18, 2004.
18. Department of Transportation, Federal Highway
Administration. Highway Statistics—2000. Available
at: http://www.fhwa.dot.gov/ohim/hs00/. Accessi-
bility verified May 14, 2004.
19. Dee TS, Sela RJ. The fatality effects of highway
speed limits by age and gender. Economic Letters.
2003;79:401-408.
20. Evans WN, Graham JD. Risk reduction or risk com-
pensation? the case of mandatory safety-belt use laws.
J Risk Uncertainty. 1991;4:61-73.
21. Eisenberg D. Evaluating the effectiveness of poli-
cies related to drunk driving. J Policy Anal Manage.
2003;22:249-274.
22. Evans WN, Graham JD. Traffic safety and the busi-
ness cycle. Alcohol Drugs Driving. 1991;4:31-38.
23. Ruhm CJ. Alcohol policies and highway vehicle
fatalities. J Health Econ. 1996;15:435-454.
24. Gruber J. The incidence of mandated maternity
benefits. Am Econ Rev. 1994;84:622-641.
25. Dee TS. The effects of minimum legal drinking ages
on teen childbearing. J Human Res. 2001;36:823-838.
26. White H. A heteroskedasticity-consistent covari-
ance matrix estimator and a direct test for heteroske-
dasticity. Econometrica. 1980;48:817-838.
27. Levy DT. The relationship of age and state li-
cense renewal polices to driving licensure rates. Ac-
cid Anal Prev. 1995;27:461-467.
28. Owsley C, McGwin Jr G. Vision impairment and
driving. Surv Ophthalmol. 1999;43:535-550.
29. Ball K, Owsley C, Stalvey B, Roenker DL, Sloane
ME, Graves M. Driving avoidance and functional im-
pairment in older drivers. Accid Anal Prev. 1998;30:
313-322.
30. West CG, Gildengorin G, Haegerstrom-Portnoy
G, Lott LA, Schneck ME, Brabyn JA. Vision and driv-
ing self-restriction in older adults. J Am Geriatr Soc.
2003;51:1348-1355.
31. Nelson DE, Sacks JJ, Chorba TL. Required vision
testing for older drivers. N Engl J Med. 1992;326:
1784-1785.
MOTOR VEHICLE FATALITIES AMONG THE ELDERLY
2846 JAMA, June 16, 2004—Vol 291, No. 23 (Reprinted) ©2004 American Medical Association. All rights reserved.