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Learning to Drive in California: Patterns in Novice Motor Vehicle Crashes and Traffic Violations in the Era of the Graduated Driver Licensing Law. Center for Healthcare Policy and Research Seminar Series. Scott Vincent Masten California DMV Research & Development Branch. Speaker’s Verbal

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scott vincent masten california dmv research development branch

Learning to Drive in California: Patterns in Novice Motor Vehicle Crashes and Traffic Violations in the Era of the Graduated Driver Licensing Law

Center for Healthcare Policy and Research Seminar Series

Scott Vincent Masten

California DMV

Research & Development Branch

slide2

Speaker’s Verbal

Disclosure Statement

Have you (or your spouse/partner) had a personal financial relationship in the last 12 months with the manufacturer of the products or services that will be discussed in this CME activity?

___ Yes

_X_No

(If yes, please state disclosures and resolutions)

slide3

Educational Objectives

for this Seminar

To describe how the crash rates of novice drivers change after licensure

To identify novice drivers with exceptionally high crash rates after the California graduated driver (GDL) licensing law was implemented

To discuss opportunities for reducing crash mortality and morbidity among age 18 and older novices

motor vehicle crashes
Why should I care?
  • Over 2.7 million injuries per year
  • Leading cause of death for ages 13-25
  • Top 5 cause of death for ages 1-44
Motor Vehicle Crashes
  • CDC, WISQARS, 2014
fatal 16 19 year old crashes united states annual
2,500 teen driver deaths (180 California)
  • 1,600 teen passenger deaths (170 California)
  • 10% of all crash fatalities are teens
Fatal 16-19-Year-Old CrashesUnited States, Annual

FARS; 2000-2009

crash rates by driver age united states 2000
Crash Rates by Driver AgeUnited States, 2000
  • Crash rates decrease as age increases
  • Highest rates among teens 16-19
  • Many teens are just learning to drive (novices)
first crash incidence each month after licensed to drive unsupervised

Novice teen crash rates decrease markedly during the first year

  • They continue to decrease at a slower rate for years
  • Even a little driving experience results in much lower crash rates
First Crash IncidenceEach Month After Licensed to Drive Unsupervised
graduated driver licensing gdl

Reduce risk while experience gained

  • Implemented in all U.S. jurisdictions
  • Restrictions on novice teen driving are gradually removed in three stages:
    • Learner Stage
      • May drive only with a licensed adult
    • Intermediate Stage
      • Unsupervised, but driving restrictions:
        • Nighttime
        • Passengers, usually other teens
    • Unrestricted (full) Driving Stage
Graduated Driver Licensing (GDL)
graduated driver licensing and fatal crashes involving 16 to 19 year old drivers

Graduated Driver Licensing and Fatal Crashes Involving 16- to 19-Year-Old Drivers

Scott V. Masten, Robert D. Foss, & Stephen W. Marshall

nationwide evaluation of gdl

Design

  • Pooled cross-sectional time series
  • Data
  • Fatality Analysis Reporting System (FARS)
    • Driver fatal crash involvements
    • Passenger vehicles
    • All states & D.C.
    • 1986-2007, quarterly
    • State-age group-quarters
  • Population data from the U.S. Census
Nationwide Evaluation of GDL
nationwide evaluation of gdl1

Analysis

  • Poisson regression with GEEs
  • Separate models ages 16, 17, 18, 19, & 16-19
  • Control for non-GDL law changes, crude exposure, economic conditions
  • Trend & seasonality adjusted by state & age
  • Adult crash rate covariates - unmeasured confounders
Nationwide Evaluation of GDL
evaluation of the california graduated driver licensing gdl program

Evaluation of the California Graduated Driver Licensing (GDL) Program

Scott V. Masten & Robert A. Hagge

Note: Originally completed in 2004; updated data presented here

the california gdl program

Implemented July 1998

  • Applies to all drivers licensed age <18
    • Learner Stage
    • Min age 15; 15½ starting 2004
      • 6 mo. mandatory learner permit
      • 50 hours supervised practice
    • Intermediate Stage (age ≥16)
        • Nighttime restriction - 12:00am-5:00am for 12 mo.
            • 11:00pm-5:00am starting 2006
          • Passengers – None < age 20 for 6 mo.
            • 12 mo. starting 2006
    • Unrestricted (full) Driving Stage
    • Min age 17; automatic at age 18
The California GDL Program
research questions

How did CA population-based teen crash rates change after GDL?

  • How did CA driver-basedteen injury crash rates change after GDL?
  • How did CA licensure rates change after GDL?
Research Questions
study data

Statewide Integrated Traffic Records (SWITRS)

    • Driver injury crash involvements
    • Passenger vehicles
    • 1985-2011, monthly
  • Population data from the U.S. Census
  • License data from DMV
Study Data
california crashes per driver

Age 17-20 increased after GDL

California Crashes, per driver
  • No decrease in age 16 crash rates per driver after GDL
study conclusions

CA crashes mirror the nationwide GDL study

    • Lower crashes for younger teens
    • Higher crashes for older teens
  • CA licensure rates after GDL:
    • Lower for ages 16-17
    • Same or higher for ages 18-20
Study Conclusions
  • What’s going on with older CA teens after GDL?
crash rates of teens delaying licensure compared with those not delaying licensure

Crash Rates of Teens Delaying Licensure Compared with Those Not Delaying Licensure

Eric A. Chapman& Scott V. Masten

study background

Nationally, GDL associated with higher 18–19-year-old fatal crash rates (Fell, Jones, Romano & Voas, 2011; Males, 2007; Masten, Foss, & Marshall, 2011; Masten & Hagge, 2003)

  • Possible mechanisms:
    • More 18–19 Novices: Delayed licensure to avoid GDL
    • Lower 18–19 Competency: GDL limits real-world driving experience
Study Background
research questions1

Do CA teens appear to delay licensure to avoid GDL?

  • How do CA teens who delay licensure drive compare to their same-age peers?
  • How do CA teens who delay licensure compare to novices of other ages?
Research Questions
method

Data

    • Random 10% of CA newly-licensed (novices), 1999–2007 (post-GDL)
    • 3-year total & fatal/injury crashes
  • Analyses
    • Age of novice CA licensure
    • Novices vs. same-age peers licensed 1 or 2 years prior
      • Separate Poisson models 18, 19, 20, 21–24, & 25–35
    • Different-aged novices vs. each other
Method
age of novice licensure 1999 2007

Most novices at 16 or 18

Fewer at 17, suggesting…

Delayed licensure until 18

Age of Novice Licensure, 1999-2007
age 18 novices vs age 18 experienced
Age 18 Novices vs. Age 18 Experienced

Licensed at 18 (avoided GDL)

Licensed at 17 (GDL)

Licensed at 16 (GDL)

Note: Rates adjusted for sex, year, & month of licensure.

age 19 novices vs age 19 experienced
Age 19 Novices vs. Age 19 Experienced

Licensed at 19 (avoided GDL)

Licensed at 18 (avoided GDL)

Licensed at 17 (GDL)

Note: Rates adjusted for sex, year, & month of licensure.

age 20 novices vs age 20 experienced

Experience associated with fewer crashes for all ages…

Ages 21-24

Age 20

Age 20+ Novices vs. Age 20+ Experienced

Novices of all ages are worse drivers than same-age peers.

  • Ages 25-35
novices of different ages total crashes

18

16

17

Even younger novices

19

20

Drop

21-24

25-35

18 novices start out worse than everyone…

Novices of Different Ages (Total Crashes)

One age group does not fit the pattern

Note: Rates adjusted for sex, year, & month of licensure.

novices of different ages fatal injury

18

19 novices also bad

19

20

Drop

17

16

21-24

25-35

Again 18 novices are worse than everyone

Novices of Different Ages (Fatal/Injury)

Does this explain the higher 18-19 crash rates after CA GDL?

Note: Rates adjusted for sex, year, & month of licensure.

research question 1

Do CA teens appear to delay licensure to avoid GDL?

Yes:

  • Fewer teens licensed at 17
  • Licensure pops up again at 18
Research Question #1
research question 2

How do CA teens who delay licensure drive compare to their same-age peers?

They have higher crash rates:

  • CA 18 and 19 year-olds who delay licensure crash more than their same-aged peers…
  • But this is true for novices of all ages compared to their same-age peers
Research Question #2
research question 3

How do CA teens who delay licensure compare to novices of other ages?

They have higher crash rates:

  • Delaying 18 year-olds have higher total and fatal/injury crash rates than other novices.
  • Delaying 19 year-olds have higher fatal/injury crash rates than other novices.
Research Question #3
study conclusions1

Some CA teens appear to delay licensure until age 18: No GDL or driver education.

  • 18-19 novices who avoid GDL are worse than ALL other novices, even younger teens
    • Was this a result of implementing GDL?
  • All novices worse than their experienced peers: GDL may benefit novices of all ages.
Study Conclusions
eric a chapman scott v masten kelly k browning

Crash and Traffic Violation Rates Before and After Licensure of Novice California Drivers Subject to Different Driver Licensing Requirements

Eric A. Chapman, Scott V. Masten, & Kelly K. Browning

study background1

When novice teens begin to drive unsupervised their crashes increase radically, even under GDL programs (Lewis-Evans, 2010; Mayhew et al., 2003; VicRoads, 2008)

  • Crash rates decrease dramatically within the first months of licensure, but remain high vs. older novices (Lewis-Evans, 2010; Masten & Foss, 2010; Mayhew et al., 2003; Twisk & Stacey, 2007; VicRoads, 2008)
  • Inexperience may cause high initial crash rates; teen rates may remain elevated because of overconfidence (Ericsson, Krampe, & Tesch-Römer, 1993)
Study Background
research questions2

How do crash and traffic violation rates of novice CA 16–17-year-old drivers licensed under GDL change over time?

  • How do the rates for novice drivers age 18 and older not licensed under GDL change over time?
  • How do the types of traffic violations vary during the course of licensure?
Research Questions
method1

Data

    • All novices licensed in CA at age 16 or 17 (2001-2007)
    • 10% sample of all age 18 to 35 novices (2001-2007)
    • 3-year post-licensure crashes and traffic violations
      • Traffic violations categorized as inexperience-related vs. overconfidence-related
  • Analyses
    • Length learner permits are held by age
    • Crash and traffic violation rates over time
      • Overall & subtypes (e.g., fatal/injury, inexperience)
    • Separate Poisson models 16, 17, 18, 19, 20, 21–24, 25–35
Method
learner permit holding by age

Majorities of age 16 (57%) and age 17 (73%) hold learner permits longer than the required 6 months

  • 31% of age 16 and 49% of age 17 hold permits for 9+ months
  • Majorities of age 18+ novices hold learner permits less than 6 months
Learner Permit Holding by Age
total crash rates

Peak rates typically 2nd or 3rd month

Age 18+ ramp-up of crashes before licensure

Total Crash Rates

Crash rates for all novices decrease most during 1st year of driving

fatal injury crash rates

Pre-licensure rates highest for age 18+

Fatal/Injury Crash Rates

Age 18 and 19 novices initially crash more than younger novices

crash rate findings

Crash rates of most novices are highest immediately after licensure

  • They decline quickly during their 1st year
  • Then decline slower for the 2nd and 3rd years

Just like classic learning curves

Crash Rate Findings
crash rate findings cont

Post-licensure crashes are higher for some age 18+ novices than those for ages 16–17

  • Pre-licensure crash rates for age 18+ novices ramp up immediately before licensure
  • Suggests they try to learn to drive during a very short time period
    • Contrary to good learning methods (spaced practice)
  • 70% of age 16–17 novices are crash-free for the first 3 years of licensure
Crash Rate Findings (cont)
total traffic violation rates

Wow

Age 18+ violations highest during 1st year or pre-license

Total Traffic Violation Rates

Traffic violations for age 16 and 17 novices peak long after their crashes, around the time when they are age 18

inexperience vs overconfidence violations

Age 16-17: inexperience & overconfidence violations peak after crashes, when they turn age 18

Inexperience

Age 18+: inexperience and overconfidence violations peak 1st year of licensure, when crashes peak too

Inexperience vs. Overconfidence Violations

Overconfidence

traffic violation rate findings

Age 16–17 novices’ traffic violation rates peak long after their crashes peak (when age 18)

  • Violation rates for age 18+ novices peak during their 1st year of licensure.
  • Inexperience and overconfidence violations typically peak around the same time
  • 45% of age 16–17 novices are traffic violation-free for the first 3 years of licensure
Traffic Violation Rate Findings
study conclusions2

Age 16–17 novices typically hold learner permits for longer than minimum 6 mo.

  • Older CA novices appear to rush learning to drive; do not hold permits very long
  • Novices driver crash rates for most ages follow a classic learning curve
  • Novice driver violation rates do not follow a classic learning curve—proxy for exposure
Study Conclusions
slide50

Review of

Educational Objective #1

To describe how the crash rates of novice drivers change after licensure

Pattern follows classic learning curve

Highest immediately after licensure

Decrease dramatically during the 1st year

Decrease at a slower rate subsequently

slide51

Review of

Educational Objective #2

To identify novice drivers with exceptionally high crash rates after the California graduated driver (GDL) licensing law was implemented

Age 18-20 crashes increased after GDL

Age 18-19 crash rates now higher than all other novices, even younger teens

slide52

Review of

Educational Objective #3

To discuss opportunities for reducing crash mortality and morbidity among age 18 and older novices

Given that age 18+ novices appear to cram learning to drive into a short period…

Maybe they would benefit from minimum learner permit holding periods

Given that age 18+ novices are also worse than their experienced peers…

Maybe they would benefit if GDL was extended to them, particularly for ages 18-20

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