Nationwide Review of GDL

Report
Nationwide Review of
Graduated Driver Licensing
Research conducted by Johns Hopkins Bloomberg School of Public Health
AAA Foundation for
Traffic Safety
• Established in 1947
• 501 (c)(3) Not-For-Profit
• Research affiliate of
AAA/CAA
• North American Focus
Mission
• Identify traffic safety problems
• Foster research that seeks solutions
• Disseminate information and
educational materials
Funded through the generosity
of
and its members
Published February 2007
Prepared by:
Johns Hopkins Bloomberg
School of Public Health
Available online at:
www.aaafoundation.org
The teen crash problem
• Motor vehicle crashes are the #1 cause of
death for teens
– Roughly 1,000 16-year-old drivers involved in
fatal crashes each year
•
•
~400 16-year-old drivers killed annually
Nearly 2 other fatalities per teen driver fatality
–
–
–
Passengers of teen
Drivers and passengers in other vehicles
Pedestrians, bicyclists, etc.
– Nearly 100,000 involved in injury crashes
(10,000+ resulting in incapacitating injuries)
Graduated Driver Licensing (GDL)
• Typical three-stage GDL program
involves:
– Learner stage – all driving must be
supervised by adult (usually parent)
– Intermediate (or “Provisional”) stage –
allows unsupervised driving but only under
certain conditions (e.g., during the day, no
passengers)
– Full License – requires successful
completion of first two stages
Purpose of study
• Analyze overall (nationwide) crash reduction
of having any three-stage GDL program
• Distinguish between effectiveness of the
most comprehensive programs and
relatively weaker programs
• Assess how much better we could be doing
if all states had the most comprehensive
programs
The Study - Data
• GDL Laws (1994-2004, all states, from
AAA, IIHS, and individual states)
• Fatal crashes (1994-2004, 43 states,
from National Highway Traffic Safety
Administration)
• Injury Crashes (1994-2003, 35 states,
obtained with permission from individual
states)
• Population estimates (all states and
years studied, from U.S. Census Bureau)
states)
The Study – Analysis
• State-quarter: crash rates and laws in one
state for one quarter-year
– e.g., “Alabama’s crash rates and Alabama’s laws
between January 1, 2000 and March 31, 2000”
is one state-state quarter
• Combined state-quarters with the same laws
to estimate overall impact of laws (1 “national”
study, not separate study in each state)
The Study – Analysis
• Statistical methods (negative binomial
regression) to control for differences
unrelated to GDL (state-to-state
differences, time trends, seasonal
variation)
• Also looked at crash rates of older drivers
(ages 20-24, 25-29, 30-54) – these
should not have been impacted by GDL
Overall impact of 3-stage GDL
programs
• Rate of fatal crashes of 16-year-olds reduced by
11% (per capita) in states with 3-stage GDL
programs
• Rate of injury crashes reduced by 19%
• Reductions much smaller (and not statistically
significant) for older drivers
• Results adjusted for state-to-state differences,
seasonal differences, and time trends
• These results include strong and weak programs,
so not representative of effectiveness of the best
programs
Percentage difference in crash rates in relation driver
age and presence of 3-stage GDL program
Fatal Crashes
Injury Crashes
10%
0%
-10%
-11%
-20%
-19%
Age 16
-30%
Age 20-24
Age 25-29
-40%
Age 30-54
Columns represent estimated
differences in crash rates,
vertical lines represent 95%
confidence intervals
(Negative means crash rate
lower with 3-state GDL
program than without)
Program comprehensiveness
•
Studied seven key components, grouped states
by how many they had
1. Minimum age of 16 for learner’s permit
2. Requires at least 6 months with learner’s permit
before intermediate or full license
3. Requires at least 30 hours supervised driving during
learner stage
4. Minimum age of 16 years 6 months for intermediate
license
5. No driving allowed after 10 PM during intermediate
stage
6. No more than 1 passenger allowed during
intermediate stage
7. Minimum age of 17 for full license
Program comprehensiveness
• No state had more than 5 of the 7 during the
study
• Fatal crashes of 16-year-olds reduced by
38%, injury crashes by 40%, in states
with 5 of the 7 components
• Reductions of 21% (fatal crashes) and 36%
(injury crashes) in states with 4 of 7
• Smaller reductions with fewer components
Percentage difference in fatal crash rates in relation to
driver age and number of program components
One
Two
Three
Four
Five
Component Components Components Components Components
30%
0%
-4%
-10%
-10%
-21%
-30%
Age 16
Age 20-24
Age 25-29
-60%
Age 30-54
Columns represent estimated
differences in crash rates, vertical
lines represent 95% confidence
intervals (Negative means crash
rate lower with number of
components shown than with none)
-38%
Percentage difference in injury crash rates in relation to
driver age and number of program components
One
Component
Two
Three
Four
Five
Components Components Components Components
30%
+3%
0%
-13%
-30%
Age 16
Age 20-24
Age 25-29
-60%
Age 30-54
-16%
Columns represent estimated
differences in crash rates,
vertical lines represent 95%
confidence intervals
(Negative means crash rate
lower with number of
components shown than with
none)
-36%
-40%
Recommendations
• States that do not yet have 3-stage GDL programs
(learner permit, intermediate license, full license)
should adopt 3-stage programs
– associated with 11% reduction in fatal crashes, 19%
reduction in injury crashes of 16-year-olds
• States should move toward implementing a full
complement of meaningful GDL program
components
– Programs with 5 components have much greater
impact than average 3-stage programs
Limitations of the Study
• GDL components studied were compromise
between existing recommendations (from AAA,
IIHS, and others) and statistical requirements—this
study does not “prove” that they are optimal
• Statistical model couldn’t control for everything,
some other factors could have influenced results
• Can’t tell how apparently effective programs work
(safer driving? less driving? both? other ways?)
• Didn’t look at older teens
For more information,
please go to:
www.aaafoundation.org
The AAA Foundation for Traffic Safety is a
501(c)(3) public charity located in
Washington, DC that is dedicated to
saving lives and reducing injuries.
It is supported by donations from
AAA/CAA Clubs, AAA/CAA members, and
other organizations associated with
AAA/CAA.

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