TEENAGE DRIVER CRASHES -- CARRYING PASSENGERS

AS A RISK FACTOR

Li-Hui Chen, MS, Ph.D.Assistant Scientist

Johns Hopkins School of Public HealthCenter for Injury Research & Policy

Readings• Carrying passengers as a risk

factor for crashes fatal to 16- and 17-year-old drivers

• Reducing fatal crash risk among teenaged drivers

• Graduated licensing: a blueprint for North America

Learning Objectives:

• Understand the scope of MV injury for teenage drivers

• Learn about the risk to teenage drivers of carrying passengers

• Learn about the GDL system

Performance Goals:

• Be able to describe the importance of MV injury for teenagers

• Be able to describe the risk of carrying passengers for teen driver

• Be able to describe the ideal GDL system

Background

For U.S. teens, MV crashes• are the leading cause of death,

accounting for 36% of all deaths• have a much higher rate than for

older drivers

Background--Haddon Matrix

Phases

Factors

Human Vehicle Environment

Precrash Carrying Passengers

CrashPostcrash

Background—GDL System

• Lets teen drivers earn experience step by step and in a less risky environment

Background--Central framework for GDLThree stages• Supervised learner’s period• Intermediate license• Full license

Background—Current GDL adoption in the U.S.• 30 states had adopted full

graduated licensing systems• 14 states had some passenger

restrictions

Methods--Data

• FARS: All fatal crashes in the U.S.• GES: Sample of police reported

crashes in the U.S.• NPTS: Survey of travel patterns in

the U.S.

Methods--Analysis

• Risk of death per 10 million trips• Risk of death per 1000 crashes• Relative risk and confidence

intervals

Results

Trip-Based Driver Death Rates

0123456

16 17 30-59

Driver Age, y

Deat

hs / 1

0,00

0,00

0 Tr

ips

No Pass1 Pass2 Pass3+ Pass

ResultsTrip-Based Risks for Teenaged Driver Deaths

6AM-9:59 PM 10-11:59 PM 12-5:59 AM

Passenger Present

No Yes No Yes No Yes

DR 1.24 2.20 3.26 6.37 14.20 21.88

RR - 1.77 - 1.95 - 1.54

Results

Driver Deaths (aged 16-17) per 1,000 Crashes

Age and Number of Passengers

Aged 13-19 Aged 20-29

None 1 >=2 1 >=2

DR 1.44 2.08 2.46 3.55 3.90

RR - 1.45 1.71 2.47 2.71

Results

Teenaged Driver Deaths per 1,000 Crashes

Sex and Number of Passengers

Female Male

None 1 >=2 1 >=2Both Sex

DR 1.44 1.56 1.59 2.54 3.19 2.63

RR - 1.08 1.11 1.76 2.22 1.83

Results-Summary

• Fatal crash rates for drivers aged 16-17 increased with the number of passengers for both day and night

• Crashes are more likely to be fatal in the presence of male, teen, and age 20-29 passengers

Discussion--Possible explanations

• Dangerous driving behaviors• Distraction• Alcohol involvement

Discussion--Limitations

• Unable to control alcohol• Do not have information on age of

passengers in travel pattern

Conclusions

Restrictions on carrying passengers should be considered for inclusion in graduated licensing systems for young drivers

Further Studies

• Age of passengers• The relationship to alcohol use• Why carrying passengers

increases risk