Young Driver Licensing in New Jersey: Rates and Trends, 2006-2011

607 14th Street, NW, Suite 201 | Washington, DC 20005 | AAAFoundation.org | 202-638-5944

Teens have the

highest crash rate

of any group in

the United States.

Young Driver Licensing

in New Jersey: Rates and

Trends, 2006-2011

July 2014

Title

Young Driver Licensing in New Jersey: Rates and Trends, 2006-2011 (July 2014)

Authors

Allison E. Curry, PhD, MPH

Melissa R. Pfeiffer, MPH

Dennis R. Durbin, MD, MSCE

Michael R. Elliott, PhD

Konny H. Kim, MPH

THE CHILDREN’S HOSPITAL OF PHILADELPHIA RESEARCH INSTITUTE

Acknowledgments

The authors would like to extend our thanks to Brian Tefft and Jurek Grabowski of the AAA

Foundation for Traffic Safety. They authors would also like to acknowledge Sayaka Ogawa

for her work on this project and the New Jersey Motor Vehicle Commission, Department of

Transportation, and Office of Information Technology for their assistance in providing data.

About the Sponsor

AAA Foundation for Traffic Safety

607 14th Street, NW, Suite 201

Washington, DC 20005

202-638-5944

www.aaafoundation.org

Founded in 1947, the AAA Foundation in Washington, D.C. is a not-for-profit, publicly supported

charitable research and education organization dedicated to saving lives by preventing traffic

crashes and reducing injuries when crashes occur. Funding for this report was provided by

voluntary contributions from AAA/CAA and their affiliated motor clubs, from individual members,

from AAA-affiliated insurance companies, as well as from other organizations or sources.

This publication is distributed by the AAA Foundation for Traffic Safety at no charge, as a

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recommendations contained in this report.

If trade or manufacturer’s names are mentioned, it is only because they are considered essential

to the object of this report and their mention should not be construed as an endorsement. The

AAA Foundation for Traffic Safety does not endorse products or manufacturers.

Table of Contents

Brief Summary ......................................................................................................................... 3

Introduction .............................................................................................................................. 4

Methods ..................................................................................................................................... 6

New Jersey GDL System ...................................................................................................... 6

New Jersey Licensing Database ........................................................................................... 6

Census Data .......................................................................................................................... 7

Study Population and Analysis ............................................................................................ 7

Results ....................................................................................................................................... 8

Intermediate Licensure ........................................................................................................ 8

Graduation to Full Licensure ............................................................................................... 8

Licensure Rate by Zip Code Level Indicators ....................................................................... 9

Trends in Initial Licensure, 2006-2011 ................................................................................ 9

Discussion ................................................................................................................................10

Conclusion ...............................................................................................................................12

References .................................................................................................................................13

Appendix – Figures 1-7 ............................................................................................................16

Brief Summary

Introduction

Recent nationally-representative surveys have provided important insight on the primary

reasons why US teens delay licensure, but are limited in their ability to estimate licensure

rates and trends. State-level administrative licensing data are the ideal data source to

provide this information, but they have not yet been analyzed for this purpose. Our

objective was to analyze New Jersey’s (NJ) licensing database to: (1) describe population-

based rates of licensure among 17- to 20-year-olds, overall and by gender and zip code level

indicators of household income, population density, and race/ethnicity; and (2) examine

trends in licensure from 2006 through 2011. The research presented here was conducted as

a part of a larger study that is examining the effects of age and experience on crash rates

among New Jersey drivers licensed at older versus younger ages.

Methods

We obtained records on all individuals who obtained a NJ driver’s license through June

2012 from the NJ Motor Vehicle Commission’s licensing database, and determined each

young driver’s age at the time of intermediate and full licensure. Residence address zip

codes were categorized into quintiles for relevant socioeconomic indicators. Data from the

US Census and 2011 American Community Survey were used to construct population

denominators and specifically to define a fixed cohort of NJ residents who turned 17 years

old in 2006–2007 (n=255,833). Licensure data were used to determine the number of drivers

who turned 17 years old in 2006–2007 and obtained an intermediate license by each month

of age (numerators) and, among those who obtained an intermediate license, time to

graduation to full licensure. Licensing rates were estimated for the overall NJ population,

as well as by gender and by quintiles of zip code level indicators for household income,

population density, and race/ethnicity. Finally, we estimated licensure rates separately for

annual cohorts of 17-year-olds from 2006 through 2011.

Results

Forty percent of all residents—and half of those who ultimately obtained a license by age

21—were licensed within a month of NJ’s minimum licensing age of 17. In all, 64 percent of

teens were licensed by their 18

birthday, 74 percent by their 19

birthday, 78 percent by

their 20

birthday, and 81 percent by their 21

birthday. Further, the younger an individual

obtained his or her intermediate license, the earlier he or she graduated to a full license.

Licensing rates were slightly higher for females than males, but we observed starkly different

patterns of licensure by socioeconomic zip code level indicators. For example, 65 percent of

17-year-olds residing in the highest-income zip codes were licensed in the first month of

eligibility, compared with 13 percent of residents living in the lowest-income zip codes.

Finally, the rate and timing of licensure in NJ has been relatively stable from 2006 through

2011, with at most a one to three percentage point decline in rates over this period.

Implications

NJ has the highest minimum licensing age in the US and is the only state in which

Graduated Driver Licensing (GDL) requirements apply to 18- to 20-year-old drivers. These

results provide a unique perspective from a state whose GDL system has long been hailed

as a model and informs stakeholders in other states as they consider raising their minimum

licensing age and/or extending GDL restrictions to older novice drivers. Our findings also

support the growing body of literature suggesting that teens delay licensure primarily for

economic reasons and that a substantial proportion of potentially high-risk teens may be

obtaining licenses outside the auspices of a GDL system. Finally, the trend in licensure

from 2006 through 2011 was relatively stable, in contrast to recent national-level reports of

a substantial decline in licensure rates.

Introduction

Prior studies have established the effectiveness of US Graduated Driver Licensing (GDL)

systems in reducing the incidence of crashes among young novice drivers, as well as the

benefit of a higher minimum licensing age.

1-3

However, GDL programs in almost all US

states include novice drivers only up to age 18. Some (but not all) recent GDL evaluations

have reported higher fatal crash rates among 18-year-old drivers,

2,4-6

raising the issue that

certain subgroups of teens may be delaying the onset of licensure to an age at which they

are no longer covered by their state’s GDL system. The young driver research community is

beginning to delve into this issue and its potential implications, and an important step in

doing so is to gain a better understanding of licensure patterns among US teens and how

these patterns vary among subgroups.

Several recent nationally-representative surveys have estimated driver licensing rates among

teens. In 2010, the annual Monitoring the Future (MTF) survey estimated that 73 percent of

US high school seniors reported having a driver’s license.

In a separate survey of 1,039 18- to

20-year-olds conducted by the AAA Foundation for Traffic Safety in 2011, 65 percent of 18-

year-olds, 70 percent of 19-year-olds, and 76 percent of 20-year-olds reported being licensed.

Studies differ in terms of whether rates vary by gender,

7-9

but lower rates were noted among

Hispanics and African-Americans compared with whites,

7,9,10

those with lower income,

and

those residing in denser urban areas compared with less dense urban areas.

The specific timing of licensure and how that has changed in recent years is largely

unknown, with only two recent surveys examining this question. Tefft et al. found that only

44 percent of teens were licensed within one year of their state’s minimum licensing age,

while McCartt et al. conducted interviews in three states (RI, NC, MN) with 16- and 17-

year-olds who presented to DMVs to take their on-road driving test, and found that most

teens obtained their license within two months of eligibility.

Although the general perception is that licensure rates have declined in the US—in

particular in the late 2000s coinciding with the economic recession—in truth, few studies

have assessed trends.

The only survey to do so showed a 12 percentage point decline in

the number of licensed high school seniors from 1996 to 2010 (85% to 73%), with two-thirds

of that decline occurring between 2006 and 2010. Notably, these reports were based on the

single question “Do you have a driver’s license?” and traversed the time period in which

states implemented GDL systems, adding to the possibility of different interpretations of

the term “driver’s license.” In addition, a Highway Loss Data Institute (HLDI) study

showed that the level of insured teens declined between 2006 and 2012.

Several reasons have been posited regarding why US teens delay licensure, including to

avoid GDL system requirements,

an increased ability to connect virtually with friends,

and the availability of alternative transportation systems.

Recent studies, however,

provide evidence that teens delay licensure primarily for economic and practical reasons.

Teens reported not having a car, the cost of gas or maintaining a vehicle, being able to get

around without driving, and being busy with other activities as main reasons for not

obtaining a license, while fewer mentioned their state’s laws or virtual connectivity with

friends.

8,16

These results, combined with findings of delayed licensure among minority and

lower-income teens and the HLDI’s finding that unemployment was a significant factor in

the decline of insured teens,

8,14

warrant further investigation of the role of socioeconomic

factors on licensing rates.

Although surveys have provided important insight on the reasons for delayed licensure,

they have significant limitations in estimating licensing rates. Their cross-sectional nature

precludes assessment of trends, national studies do not always account for differences in

minimum licensing ages across states and may include respondents from only a fraction of

states, sample sizes may preclude examination of subgroup differences, and teens may have

to recall age at licensure. Further, cumulative proportions of time to licensure estimated by

McCartt et al. were conditional on 16- and 17-year-olds having presented at the DMV for a

road test—that is, rates were estimated among 16- or 17-year-olds seeking licensure

instead of the entire population of 16- and 17-year-olds (the denominator of interest).

Analysis of population-level licensure data would overcome the above-mentioned

limitations and complement in-depth surveys by providing information on the timing of and

trends in teens’ licensure. Thus far, only aggregate data provided by the Federal Highway

Administration (FHWA) has been used to provide population-level licensure estimates.

Using FHWA data, Sivak and Schoettle reported that 76 percent of US 19-year-olds were

licensed in 2008 and that by 2010 the proportion had declined to 70 percent.

However,

serious concerns have been raised about the validity of FHWA data, and large year-to-year

fluctuations in the number of licensed 16-year-olds have been reported in FHWA data for at

least a dozen states.

18,19

State-level administrative licensing data serve as the ideal source for population-based data

on licensing but have not yet been analyzed for this purpose. To this end, we aimed to

utilize New Jersey’s (NJ) state licensing database to describe population-based rates of

licensure among 17- to 20-year-olds. New Jersey is unique in that its minimum licensure

age of 17 is the highest of any US state, and it is the only state for which full GDL

requirements apply to all newly-licensed drivers under 21 years of age. While this limits

the immediate generalizability to other states, it does provide a unique perspective from a

state whose GDL system has long been hailed as a model, and informs stakeholders in

other states as they consider raising their minimum licensing age and/or extending GDL

restrictions to older novice drivers.

In addition, these analyses serve as an illustration of

the types of data that may be extracted from state licensing databases to further advance

young driver research. Specifically, our objectives were to: (1) determine the proportion of

NJ residents who obtain an initial (intermediate) license by each month of age (17 through

20), both overall and by gender and zip code level indicators of household income,

population density, and race/ethnicity; (2) describe rates of graduation from intermediate to

full licensure; and (3) examine trends in licensure rates from 2006 through 2011.

Methods

New Jersey GDL System

New Jersey has one of the most comprehensive GDL laws in the US (enacted in 2001), with

the highest minimum age of licensure, and one of the lowest teen crash fatality rates.

Adolescents progress through three licensing phases:

(1) Learner’s permit: eligible at a minimum age of 16 (17 if no formal driver training)

and 180-day minimum holding period;

(2) Intermediate license (known as probationary in NJ): eligible at a minimum of age

17, 365-day minimum holding period, and subject to the following restrictions:

(a) one-passenger limit unless a parent/guardian is in the vehicle;

(b) ban on driving from 11:01 p.m. through 4:59 a.m.;

communication devices; and

(d) required seat belt use for all vehicle occupants; and

(3) Full (basic) license: eligible at a minimum of age 18 following completion of

phases 1 and 2.

NJ is the only state that applies full GDL rules to all newly-licensed drivers under age 21;

in other states, newly-licensed drivers aged 18 and older are exempt from GDL

restrictions.

Note that graduation to a NJ full license is not automatic after 365 days;

drivers remain in the intermediate license phase until they present to a NJ Motor Vehicle

Commission to transition to a full license.

New Jersey Licensing Database

We obtained detailed records on all individuals who obtained a NJ driver’s license through

June 2012 from the NJ Motor Vehicle Commission’s (MVC) Licensing and Registration

Database. The database includes key data elements related to each driver’s progression

through the state’s licensing process, including exact date of birth, start dates of the permit

and intermediate license phases, date of death, and type and date of all license-related

transactions (i.e., initial, renewal, duplicate, change, upgrade, downgrade). We used these

data elements to construct each driver’s exact age at the time of intermediate and full

licensure. While the exact date of intermediate licensure was available, no specific variable

indicated the start date of the full license. Given that the minimum holding period for an

intermediate license is 365 days, we defined the start date of the full license period as the

date of the earliest license-related transaction (excluding downgrades and duplicates) that

occurred at least 365 days after the date that the intermediate period began.

Census Data

To construct population denominators, we obtained from the US Census the estimated

number of 17-year-old NJ residents in each year 2006 through 2011.

22,23

Zip code level

population estimates were available from the 2011 American Community Survey (ACS),

but only for a five-year time period (2007-2011) and for 15- to 19-year-olds combined.

estimate the number of 17-year-olds residing in each NJ zip code, we first used 2007-2011

Census population estimates to determine that 17-year-olds accounted for 21.2 percent of

NJ’s population of 15- to 19-year-olds; we then applied this proportion to ACS zip code level

15- to 19-year-old estimates. Finally, we used the 2011 ACS and 2010 Census Gazetteer

Files to categorize NJ zip codes into the following quintiles:

Categories

Quintiles

Income

(median

household)

≤$57,226

$57,227 –

$72,857

$72,858 –

$87,222

$87,223 –

$105,888

≥$105,889

Population

Density

(people per

square mile)

≤408.6

408.7 –

1223.6

1223.7 –

2615.8

2615.9 –

4876.8

≥4876.9

Racial

Distribution

(% of residents

who are non-

Hispanic white)

≤20.9%

21.0% –

65.5%

65.6% –

80.1%

80.2% –

88.8%

≥88.9%

It is important to note that New Jersey is a highly urbanized state—it has the highest

population density and ranks third in median household income.

25-27

Study Population and Analysis

The primary aim of this study was to longitudinally describe population-level licensing

rates among 17- to 20-year-old NJ residents. Our study population of interest was a fixed

cohort of NJ residents who turned 17 years old in 2006–2007. We defined this population as

the combined 2006-2007 Census estimate of 17-year-old residents in NJ (n=255,833)

and

assumed a stable rate of NJ teens entering and exiting their 17

year of life. These specific

years were selected for two reasons: (1) to ensure complete follow-up through age 20 for

each member of the study population, and (2) we discovered during our data management

process that available data on license phase was not valid for 19- and 20-year-old drivers

prior to 2006 due to a series of changes to the structure of NJ’s licensing database.

Licensure data was used to determine the number of drivers who turned 17 in 2006–2007

and obtained an intermediate license by each month of age (numerators). Finally, we

estimated age-specific licensing rates—that is, the proportion of NJ residents who turned

17 in 2006–2007 that obtained a license at each month of age. Rates were further stratified

by gender and by quintiles of zip code level indicators for household income, population

density, and race/ethnicity. We use specific notation to indicate age at licensure: for

example, licensure at 17 years and 0 months old will be notated as “17y0m” and represent

those who were licensed between their 17

birthday and one day prior to the same day in

the subsequent month.

Analyses of graduation to full licensure were further restricted to individuals who turned

17 years old in 2006 and who obtained an intermediate license before age 20. This was to

ensure we had sufficient data to follow drivers with intermediate licenses for at least 12

months after they were eligible to graduate to a full license—i.e., at least 24 months after

intermediate licensure. Follow-up time was defined as the number of months since a driver

became eligible to graduate to full licensure. The first month of eligibility was calculated as

the period spanning from 365 days after date of intermediate licensure to one day prior to

the same day in the subsequent month—e.g., for an individual licensed on January 15,

2006, the first month of eligibility includes the period from January 15, 2007 through

February 14, 2007. Individuals who died during the 24 months after intermediate licensure

without having graduated to a full license were excluded from these analyses.

Finally, we examined licensing trends over time by estimating intermediate licensure rates

separately for annual cohorts of 17-year-olds from 2006 through 2011. To estimate licensure

rates among NJ residents who turned 17 years old in 2006, for example, we used the

number of residents who turned 17 years old in 2006 (estimated from the Census) as the

denominator and the number of drivers who turned 17 years old in 2006 and obtained an

intermediate license by each of the specified ages as the numerators.

Results

Intermediate Licensure

Figure 1 (Appendix) depicts the proportion of teens licensed during each month of age from

17 through 20 years old; cumulative proportions are shown for all drivers and separately for

each gender. Overall, 40 percent of all residents—and 49 percent of those who ultimately

obtained a license by age 21—were licensed in their first month of eligibility (17y0m).

Three percent or less were licensed in each subsequent month with the exception of 17y6m

(5.2%), the minimum licensing age for those who did not complete formal driver training. In

all, 64 percent of teens were licensed by their 18

birthday, 74 percent by their 19

birthday, 78 percent by their 20

birthday, and 81 percent by their 21

birthday. The

median age at licensure for those who obtained their license by their 21

birthday was 17.1

(interquartile range [IQR]: 17.0, 17.9). Licensing rates were slightly higher for females than

males, with 41 percent of females and 38 percent of males licensed in their first month of

eligibility, and 82 percent of females and 80 percent of males licensed by their 21

birthday.

Graduation to Full Licensure

Among those who turned 17 years old in 2006 and obtained an intermediate license before

age 20, we determined the proportion that had graduated to full licensure by each month of

eligibility. As shown in Figure 2 (Appendix), graduation rates varied by age at intermediate

licensure. In general, the younger an individual obtained their intermediate license, the

more likely they were to graduate to a full license immediately upon being eligible to do so.

While 42 percent of teens who obtained their intermediate license in the first month of

eligibility (17y0m) also graduated to their full license within the first month of eligibility

(i.e., at 18y0m), only 18 percent of teens licensed at 18 years old and 15 percent of teens

licensed at 19 years old graduated to a full license as soon as they were eligible. At 12-

months post-eligibility (i.e., 24-months after intermediate licensure), 76 percent of drivers

licensed at 17y0m, 65 percent of drivers licensed at 17y1m – 17y5m, 58 percent of drivers

licensed at 17y6m – 17y11m, and 50 percent of drivers licensed at 18 or 19 years old had

graduated to a full license.

Licensure Rate by Zip Code Level Indicators

We observed substantial variations when we estimated licensure rates within populations

defined by quintiles of zip code level indicators. The proportion of residents licensed in their

first month of eligibility was much higher in high-income areas (Figure 3, Appendix); 65

percent of 17-year-olds residing in the highest-income zip codes were licensed in the first

month of eligibility compared with 13 percent of residents living in the lowest-income zip

codes. By 18 years old, the proportion licensed increased to 87 percent in the highest-

income areas but only to 36 percent in the lowest-income areas. By age 21, 39 percent of

residents in low-income areas had yet to be licensed. Similar trends were observed when zip

codes were categorized by population density and racial distribution, although the

difference was less pronounced for population density (Figures 4 and 5, Appendix).

Regarding graduation to full licensure, the proportion of drivers who transitioned in their

first month of eligibility was higher for males than females (34% vs. 29%, respectively) and

for those living in higher-income areas (36% in highest-income areas vs. 22% in lowest-

income areas) (Figures 6 and 7, Appendix). After 12 months of eligibility (24 months post-

intermediate licensure), 27 percent of those in the highest-income areas and 44 percent in

the lowest-income areas still had not graduated to a full license.

Trends in Initial Licensure, 2006-2011

Finally, we estimated the proportion of NJ residents who obtained their intermediate

license separately for yearly cohorts 2006 through 2011. For later cohorts, the end of the

study period occurred before all cohort members reached the specified birthdays;

incomplete follow-up is indicated with grey boxes. Over the study period there was at most

a one to three percentage point decline in the percent of NJ teens who obtained their

intermediate license (Table 1). In addition, the average monthly number of newly-issued NJ

intermediate licenses did not appear to change appreciably over time (Table 2). Finally, the

median age at intermediate licensure (among those licensed by age 21) was the same in

2006 and 2012 (17.1, IQR: 17.0, 17.8).

Table 1. Proportion of NJ residents obtaining their intermediate license by specified ages,

by year of 17

birthday.

Proportion of NJ teens obtaining intermediate license by…

Year of

birthday

17y0m

birthday

All

2006

2007

2008

2009

2010

2011

Table 2. Mean number of NJ intermediate licenses issued per

month to NJ 17- to 20-year-olds, by year.

Year

Mean

2006

8409

2007

8653

2008

8628

2009

8500

2010

8257

2011

8449

Jan-Jun 2012

8440

Discussion

This study utilized state-level administrative licensing data to describe the licensing

trajectory of a cohort of young NJ residents as they became eligible for licensure. Of NJ

residents who became eligible for licensure (i.e., turned 17 years old) in 2006 or 2007, 40

percent—and half of those ultimately licensed by age 21—obtained a license in the first

month they were eligible. However, a notably different picture emerges when licensing

rates are estimated within varying sociodemographic strata. Among residents living in NJ’s

highest-income zip codes, 65 percent are licensed immediately upon turning 17, and 78

percent are licensed within six months. Conversely, only 13 percent of those in the lowest-

income areas are licensed in their first month of eligibility; six months later, only 19

percent are licensed. While almost all residents in the highest-income areas are licensed by

age 21, one in three residents in the lowest-income areas are not licensed by 21. Finally,

contrary to reports of significant national declines in licensure, our results indicate that the

rate and timing of licensure in NJ have been relatively stable since 2006.

Although results of this study aren’t directly comparable to previous cross-sectional surveys

of national samples given that NJ’s minimum licensing age is higher than all other US

states, they do provide a glimpse of what licensing patterns may look like under a higher

minimum licensing age. Our finding that 64 percent of all teens are licensed by one year

post-eligibility is higher than the AAA Foundation’s national estimate of 44 percent.

This

may suggest that, compared with other states, NJ teens may get licensed at a quicker rate

once they are able to do so, perhaps in part due to the older age at which they begin the

process. Indeed, Preusser et al. reported similar results in a 1993 survey of teens in high

schools in NJ, CT, NY, and DE; by 17 years and 2 months, the rate of licensing in NJ had

surpassed rates in NY and CT, both of which had minimum licensing ages of 16 years and 7

months.

Interestingly, our age-specific estimates of the proportion of NJ teens licensed are

only a few percentage points lower than the rate reported in a survey of 10,237 NJ high

school students conducted by Williams et al. over 30 years ago,

suggesting that NJ’s GDL

implementation has not substantially altered its patterns of licensure (proportion of 17-

year-olds licensed: 67% in 1983, 64% in 2006–2007; proportion of 18-year-olds licensed: 77%

in 1983, 74% in 2006–2007).

Our findings support the growing body of literature suggesting that teens’ delay of licensure

is related primarily to socioeconomic factors. In addition to the vastly different licensing

rates by socioeconomic status found in this study and the AAA Foundation for Traffic

Safety’s national survey,

we also previously reported much lower rates of formal driver

education among minority teens in the US.

Findings in this study may be partly

attributable to the fact that NJ teens who do not complete formal driver education are

eligible for licensure six months later (at 17y6m) than those who do. On a national scale,

the findings of higher licensing ages and lower rates of formal driver training among

minorities and those of lower socioeconomic status may have important safety implications.

In all states except NJ, newly-licensed 18- to 20-year-old drivers are not subject to full GDL

requirements. Tefft et al. estimated that 75 percent of US drivers with a household income

<$20,000 are licensed after their 18

birthday,

suggesting that a substantial proportion of

low-income or minority young drivers

31-33

—who may already have higher rates of risky

driving behaviors and crashes—are becoming licensed outside the auspices of a GDL

system. This may help to partly explain findings that, in contrast to white and African-

American drivers, GDL did not significantly affect the fatal crash rate of young Hispanic

drivers.

Further, this may indicate a potential benefit of extending GDL requirements to

18- to 20-year-old novice drivers.

As Williams noted,

several states have recently considered raising their minimum

licensing ages, although no such legislation has passed. NJ teens and their parents have

recently expressed strong support both for NJ’s licensing policies and its minimum

licensing age,

although NJ is a highly urbanized state and certainly has better access to

other modes of transportation than might exist in more rural states. However, even in

national samples, the majority of parents of 15- to 18-year-olds and 18- to 20-year-olds

supported a minimum licensing age of 17 years old or higher.

8,10

Our study is meant to serve as a high-level description of licensing rates among NJ teens.

Individual-level income and race were not collected, and thus results depicting licensing rates

by zip code level indicators should not be interpreted as an investigation of the contribution of

individual-level sociodemographic factors on time to licensure. Further, zip code level

indicators were moderately correlated (range of correlation coefficients: -.53 to .43); our study

was not designed to assess the independent effects of these indicators. In addition, we were

not able to account for migration out of NJ of individuals who turned 17 years old in 2006-

2007; a resident of NJ who left the state before licensure would be accounted for in Census

denominator but not in licensing data, leading to an underestimation of the licensure rate.

Individuals who moved into NJ with a full license from another state are not included in the

numerator or denominator. Finally,

each driver’s zip code of residence reflects their address

at the time it was last updated with the NJ Motor Vehicle Commission (as of June 2012),

which is not necessarily the same as it was at the time of licensure. However, the vast

majority of drivers included in our study either had only one address since licensure (67%) or

had multiple addresses that were all in the same zip code quintile (23%).

Conclusion

Our study is unique in its use of state-level administrative licensing data to describe

licensing patterns over the course of adolescence and over calendar time. Overall, more

than three in four NJ residents were licensed by age 21, and half of those who obtained a

license by age 21 did so immediately upon turning 17 years old. Although licensure rates

did not differ greatly for males and females, starkly different patterns of licensure were

observed by socioeconomic areas. There may be important safety implications nationally if a

substantial proportion of low-income and/or minority teens is licensed between 18 and 20

years old, when GDL programs no longer apply. Finally, in contrast to recent national-level

reports of a substantial decline in licensure rates, the rate of licensure in NJ has been

relatively stable (one to three percentage point decline) from 2006 through 2011.

State licensing data provides valuable information that, in conjunction with results from in-

depth surveys, advances our understanding of US driver licensing patterns. In addition,

licensing data allows for estimation of per-driver crash rates and for examination of young

driver rates by level of experience instead of relying on age as a proxy.

A forthcoming AAA Foundation report will build on the information presented here to

investigate the independent and combined effect of age and experience on crash rates

among NJ’s young drivers licensed at older versus younger ages.

References

1. Ulmer, R. G., Ferguson, S. A., Williams, A. F., & Preusser, D. F. (2001). Teenage

crash reduction associated with delayed licensure in Connecticut. Journal of Safety

Research, 32(1), 31-41.

2. McCartt, A. T., Teoh, E. R., Fields, M., Braitman, K. A., & Hellinga, L. A. (2010).

Graduated licensing laws and fatal crashes of teenage drivers: a national study.

Traffic Injury Prevention, 11(3), 240-248.

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Appendix – Figures 1-7

Figure 1. Percent and cumulative proportion of residents obtaining a NJ intermediate license by

each month of age, among those who turned 17 years old in 2006-2007.

Figure 2. Proportion of drivers with a NJ intermediate license who obtained their full license

at each month of eligibility, by age at intermediate licensure, among those who turned 17

years old in 2006.

100

Overall percent

Overall cumulative proportion

Males

Females

100

Months Since Eligible for Full Licensure

17y0m

17y1m - 17y5m

17y6m - 17y11m

18y

19y

Age at intermediate license

Figure 3. Licensing rates among NJ residents who turned 17 years old in 2006 and 2007, by

month of age and quintiles of zip code level income.

13%

38%

49%

56%

65%

12%

13%

17%

18%

14%

12%

13%

11%

39%

14%

100

17y0m

17y1m-5m

17y6m-11m

18y

19y

20y

No license

by age 21

n = 76,556

n = 45,604

n = 42,960

n = 48,534

n = 39,426

Lower income  Higher income

Figure 4. Licensing rates among NJ residents who turned 17 years old in 2006 and 2007, by month

of age and quintiles of zip code level population density.

51%

55%

45%

17%

13%

11%

16%

14%

12%

14%

16%

13%

14%

36%

100

n = 19,246

n = 43,076

n = 51,930

n = 56,862

n = 82,722

17y0m

17y1m-5m

17y6m-11m

18y

19y

20y

No license

by age 21

Lower population density  Higher population density

Figure 5. Licensing rates among NJ residents who turned 17 years old in 2006 and 2007, by month

of age and quintiles of zip code level racial distribution (proportion of residents who are non-Hispanic

white)

18%

30%

52%

62%

67%

10%

12%

13%

15%

17%

12%

13%

12%

36%

23%

12%

100

n = 63,676

n = 73,072

n = 51,382

n = 42,018 n = 23,688

17y0m

17y1-5m

17y6-11m

18y

19y

20y

No license

by age 21

2% 2%

Lower % of non-Hispanic white residents  Higher % of non-Hispanic white residents

Figure 6. Rates of graduation to full licensure among NJ residents who turned 17 years old in 2006

and obtained an intermediate license before age 20, by months since eligible and gender

29%

34%

24%

11%

36%

31%

100

Female

Male

n = 48,561

n = 51,128

Graduated within

1 month of eligibility

Within 2-6 months

Within 7-12 months

Did not graduate

within 12 months

Figure 7. Rates of graduation to full licensure among NJ residents who turned 17 years old in 2006

and obtained an intermediate license before age 20, by months since eligible and quintiles of zip code

level income

22%

30%

34%

38%

36%

21%

22%

24%

25%

27%

13%

11%

10%

44%

36%

31%

27%

100

Did not

graduate

within

12 months

Within 7-12

months

Within 2-6

months

Graduated

within

1 month of

eligibility

n = 21,617

n = 19,228

n = 18,817

n = 21,719

n = 18,242

Low income area  High income area