motor vehicle crashes in older drivers thomas songer, phd university of pittsburgh

Motor Vehicle Crashesin Older Drivers

Thomas Songer, PhDUniversity of Pittsburgh

Learning Objectives

• Understand the current evidence regarding crash risks in older drivers

• Identify the two concerns that licensing authorities seek to balance in older drivers

• Introduce the study of medical conditions as causal agents in crashes

“Texas police say a 92-year-old driver took a wrong turn on her way to exchange a pair of shoes and ended up on the tarmac of Houston Gulf Airport, where she crashed into a Piper plane taxiing toward the runway. No one was seriously hurt.”

What is the crash risk relatedto older drivers? Howimportant is this risk?

Number of Licensed Drivers

Age

mil

lion

s of

dri

vers

16 25 35 45 55 65 75 85+

0

5

10

15

20

25

NHTSA, FHWA

Crash Involvement Rate

Age

per

1000

lice

nsed

dri

vers

16 25 35 45 55 65 75 85+0

50

100

150

200

NHTSA, FHWA

Total Miles of Travel

Age

mil

lion

s of

mil

es

16 25 35 45 55 65 75 85+0

50

100

150

200

250

300

350

NHTSA,FHWA

Involvement Rate by Mileage

Age

per

100

mil

lion

mil

es V

MT

16 25 35 45 55 65 75 85+0

500

1000

1500

2000

NHTSA, FHWA

Fatality Rate

Age

per

100

mil

lion

mil

es

16 25 35 45 55 65 75 85+0

2

4

6

8

10

12

NHTSA, FHWA

Injuries and Fragility

0

20

40

60

80100

00-0

405

-- 14

15-2

4

25-4

4

45-6

4

65-U

P

Age

Rat

e p

er 1

00,0

00 p

er y

ear

Injury RateMortality Rate

Fatal Accidents of Older Drivers

0

10

20

30

40

50

60

70

80

90

26-40 65+Age Group

Per

cent

age

Rear-endHead-onCrossing

05

101520253035404550

16 20 25 30 35 40 45 50 55 60 65 70 75 80 85

Age

per

cen

t ci

ted

for

infr

acti

on

SpeedingNot Paying AttnFailure to YieldNo proper lane

Violations in Fatal Accidents by Age

Growth of the Elderly Population

Year

num

ber

(mil

lion

s)

1950 1960 1970 1980 1990 2000 2010 2020 20300

5

10

15

20

25

30

35

65-74 yrs75-84 yrs85+ yrs

Car Trouble

Older Drivers Pose Growing Risk on Roads as their Numbers Rise

They Crash More Than Many, Yet Taking Away Wheels Leads to

Isolation, Anger

Wall Street Journal, October 29, 1993

With no standard method to pinpoint dangerous elderly drivers and get them off the roads, perhaps the best that many states can do is to simply encourage people to anonymously report bad drivers. Yet many people are loathe to do so. One such person says she still feels guilty about a woman she turned in a few years ago.

Slide 1 0f 3

The woman, who was in her early 80s, drove poorly and often left her car parked halfway in the street. Her neighbor pointed out the problem, but the woman always said she was too tired to park again. Worried that the woman might kill someone, the neighbor called the police.

Slide 2 of 3

Soon after, state officials retested the woman and revoked her license. Without her wheels, the woman was forced to move into a nursing home, where she subsequently died. “She was crushed” over losing her license,” The neighbor recalls, “I did feel responsible.”

Slide 3 of 3

Relation between Social Activities and Driving Habits in Women

Transportation Mode

56.7*63.6*80.9% club members

96.593.6*99.0% who leave house weekly

52.754.0*61.1% >3 close friends

64.3*85.3*78.5% seeing children

Other ModeOthers DriveDrives SelfSocial Activity

Huntley et al. 1986

"Officials Try to Balance Public SafetyAgainst the Rights of Older Drivers"

Crash Risk

Social Opportunities

New York Times, May 4, 1992

Licensing Older Drivers in the USA

No age provisions More frequentlicense renewals

Require testing(road or vision)

Source: IIHS(June 2001)

Issues for Appropriate Licensing

• Does licensing reduce crash involvement?

• Can high risk drivers be identified by licensing agencies?

• Are screening tests feasible?

• What is an acceptable risk for crashes?

• How many drivers would be affected?

• What are the social costs to the driver of being denied a license?

“legislatures and public agencies are frequently under pressure to

restrict drivers with medical characteristics presumed to be a

hazard to driving”

Haddon, Baker 1981

Relative risk of motor vehicle collision injury by selected cardiovascular conditions

Odds Ratio

% prevalencein

Cases Controls (95% CI)

Coronary heart diseaseMyocardial infarction 7.3 6.1 1.2 (0.6-2.3)Angina pectoris 19.7 14.1 1.5 (0.9-2.2)Coronary-artery bypass 2.6 1.6 1.6 (0.6-5.0)Any of above conditions 21.4 15.5 1.4 (1.0-2.2)

Koepsell 1994

Relative risk of motor vehicle collision injury by selected neurological conditions

Cerebrovascular diseaseStroke 1.7 2.2 0.8 (0.2-2.5)Transient Ischemia 3.0 1.8 1.6 (0.5-4.8)Either of above 4.7 3.8 1.2 (0.5-2.6)

Dementia 1.3 0.4 2.8 (0.4-17.0)Head Injury 0.9 0.2 4.0 (0.4-44.0)

Koepsell 1994

Odds Ratio

% prevalencein

Cases Controls (95% CI)

Relative risk of motor vehicle collisioninjury by selected medical conditions

Condition

Fall in previous year 12.4 9.2 1.4 (0.9-2.4)Alcohol abuse 3.4 5.6 2.1 (0.8-6.0)COPD 9.8 9.9 0.9 (0.5-1.6)

Osteoarthritis 53.8 52.0 1.1 (0.8-1.5)Rheumatoid arthritis 2.1 1.3 1.6 (0.5-5.3)Cancer 18.4 17.9 1.0 (0.6-1.5)Diabetes mellitus 11.1 4.5 2.6 (1.4-4.7)

Koepsell 1994

Odds Ratio

% prevalencein

Cases Controls (95% CI)

Research Issues

• Which population

• Exposures

• Definition of Crashes

• Recall bias

• Reporting bias

Reasons for StoppingDrivng in the Elderly

Advancing Age

Increasing Number of Factors from above

Medical ImpairmentActivity Limitation

Marottoli, 1993

Low Income

Prevalence of Driving Cessation by Age

010203040506070

70-74 75-79 80-84 > 85Age

Pre

vale

nce

%

Future Research - National Agenda

Establish Crash Risk for Medical Conditions

Document consequences of driving cessation

Improve vehicle crashworthiness for elderly

Identify causes of crashes at intersections

Examine physician role in licensing

Examine voluntary reporting of drivers

Examine how older drivers compensate for limitations