Transcript No Slide Title

Age and driving
www.automoblog.
net: an example of
the prejudice
against elderly
drivers that is
largely
unsupported by
scientific
research...
"Egon", at Automoblog, goes on to say:
"...banning old people from driving completely
seems a little bit extreme. But what about people
who can’t react in a timely manner, can’t make
reasonable decisions, and can’t see or hear as well
as other drivers? Allowing them on the road as
freely as anybody else is as ridiculous as allowing
drunk drivers on the road...
...I propose that beginning at age 65 (maybe 70), the
driver takes a strict driving test every year.
Obviously this will keep the dangerous ones off the
road, and the competent ones can still drive".
The case of
George Weller:
How risky are elderly drivers?
What kinds of problem do elderly drivers have?
What kinds of accidents do they have?
How can risky elderly drivers be identified?
How risky are elderly drivers?
Preusser et al (1998): FARS data. 65-69 year-olds are
1.45 times more likely to have a fatal accident than 4049 year-olds.
Evans (1988): data from FARS and Nationwide
Transportation Study used to calculate fatal crashes
per unit distance travelled.
Compared to 40 year-olds, 65 year-old male drivers
had 33% more fatal crashes, 65 year-old female
drivers had 77% more.
Complications in assessing elderly drivers' level of
risk:
Frailty:
Older drivers are more easily killed in an accident
(e.g. Sjöjren et al 1996, Li et al 2003).
Exposure to risk:
No good detailed statistics on different age-groups'
driving behaviour.
Problem of assessing exposure to risk:
Elderly drivers drive less, prefer
familiar roads and low speeds, avoid
night driving, heavy traffic and difficult
situations.
Therefore might be even riskier than
statistics suggest.
I'm doing 25,
that should
be fast
enough for
anybody!
Hakamies-Blomqvist, Raitenan and O'Neill (2002):
Apparent increased accident rate for elderly drivers is
an artefact.
Calculating accident rates per unit distance travelled
ignores the fact that high-mileage drivers do most of
their mileage on high-speed roads (which are safer).
Therefore elderly drivers might be less risky than the
statistics suggest!
Typical accident patterns of elderly drivers:
Hakamies-Blomqvist (1994, 1995):
More likely to be involved in collisions (ROW violations).
Less likely to have single-vehicle accidents.
Less likely to speed, drink-drive, commit major violations.
Keltner and Johnson (1987):
ROW violations increase from age 50.
Turn violations increase from age 65.
Stop sign violations show U-shaped
function - common in young and 60+.
Speeding decreases linearly with age.
Verhaegen (1995): data on 2,400 two-car collisions in
Belgium.
For each age-group, obtained "over-involvement
ratio" number of at-fault drivers/ number of blameless
drivers.
50+ year-old drivers more likely to be responsible for
their collision than 23-49 year-olds.
For 9/10 accident types, over 50's more likely to be at
fault than to be the victim.
Preusser et al (1998):
Compared to 40-49 year olds, 65-69 year-olds were
over twice as likely to be involved in a crash at an
intersection, 1.29 times more at risk in all other
situations.
85+ were 10.62 and 3.74 times as likely.
Most common error was "ran traffic control" - failing
to stop or give way. Accounted for over half of all fatal
accidents for drivers aged 74+.
Compared to 40-49 year-olds, 65-69 year olds were
twice as likely to be involved in ROW violation at an
intersection.
85+ year olds were 34 times as likely.
Daigneault, Joly and Frigon (2002):
Accident and conviction records of 426,000 Quebec
drivers aged 60-80+.
Crashes due to violations decrease with age, crashes
due to errors increase.
Elderly drivers take less risks (speeding, overtaking)
but have more problems at junctions.
Healthy and unhealthy elderly drivers:
Hakamies-Blomqvist (1996):
Normal healthy ageing is not associated with a
significant decrease in driving ability.
Ageing increases the risks of experiencing health
problems (visual pathology, dementia, etc.).
Ball et al (1998):
A subset of impaired drivers, at greater risk of an
accident, inflate the crash risk for the entire agegroup.
Evans (1993):
Need to distinguish between age and cohort effects.
Why are elderly drivers more at risk? Visual problems?
Both natural and pathological eyesight deterioration occurs
with age (e.g. presbyopia, glaucoma, hemianopia).
Davison and Irving (1980):
1400 drivers: mean acuity
at 20 yrs = 6/4.2,
at 70 = 6/7.3,
still good enough for
driving
(legal limit is roughly 6/9
in U.K.: Drasdo and
Haggerty 1981).
Percentage of drivers in each agegroup failing to meet various levels of
Snellen acuity:
Why are elderly drivers more at risk?
Attentional problems?
Useful Field of View test (e.g. Owsley et al 1991; Ball
et al 1993). UFOV score correlates better with "at
fault" accident rates, than do other measures of visual
performance.
Suggests elderly drivers may be
less able to distribute their
attention to different parts of the
visual field.
Why are elderly drivers more at risk?
Information processing problems (cognitive slowing)?
Cerella (1985), Salthouse (1991, 1996):
Age leads to slower processing speed, which leads to
impaired performance (in both speed and accuracy).
Differences are small in absolute terms.
Wood and Troutbeck (1995):
Effects of simulated visual impairment on driving, in
young and old drivers.
Goggles simulated effects of cataracts, visual field
restriction, monocular loss.
Older drivers affected more than younger drivers implying former's deficits are not solely due to visual
impairment, but lie elsewhere (cognitive slowing?)
Hole (2007): cognitive slowing as an explanation of junction
accidents:
Driving is a hierarchy of operations (Rasmussen 1983).
Operational and strategic levels unaffected in elderly.
Cognitive slowing mainly affects tactical level - but since
driving is largely self-paced, elderly can cope by driving
slower and more cautiously.
However, junctions demand effective attention and rapid
information-processing.
The "window of
opportunity" for
emerging at a junction
Hakamies-Blomqvist (1996): intersections and ageing:
Functional
domain
Task demands
Age-related change
Motor
performance
Do complex vehicle-handling
movement sequences swiftly,
while attending to traffic.
Motor slowing. Seriality in
movement organisation.
Perception
Detect objects in peripheral
vision.
Perceive movement.
Estimate own and other's
speed.
Visual field shrinking,
Decreased dynamic acuity.
Speed estimates for selfperformed actions may be
outdated.
Attention
Divide attention between
environment and car handling,
focus on task-relevant aspects
of traffic
Difficulties in divided
attention tasks, selective
attention tasks, ignoring
irrelevant information.
Interaction
Predict other's behaviour and
with other road behave predictably.
users
Slowness in approaching
intersections
misinterpreted as reflecting
intention to give way.
How can unfit elderly drivers be identified?
Many elderly drivers have insight into their problems and
restrict their driving to conditions they can cope with.
Up to 45% of dementia patients continue to drive (e.g.
O'Neill et al 1992, Lucas-Blaustein et al 1988).
Dobbs, Heller and Schopflocher (1998):
Driving test focusing on lane changes and traffic merging.
Failed by 3% of young normal, 25% of elderly normal and
68% of elderly early dementia drivers.
Demented group made many more hazardous errors: 50%
occurred while changing lanes, merging with traffic or
approaching an intersection; 21% during left turns; 15%
due to failing to stop at an intersection.
Marottoli and Richardson (1988):
Relationship between self-ratings of confidence and driving
performance (accidents and violations) in 126 drivers aged
77+. 50 of these drivers also had a driving test.
None rated themselves as worse than their peers.
32% rated themselves "the same as" their peers.
44% rated themselves "a little bit better than" their peers.
24% rated themselves as "much better than" their peers.
Actually no relationship between accident /violations
record and self-rated driving ability.
Marottoli and Richardson (1988):
"Despite the fact that 40% of the cohort reported a history
of adverse events, and 27% of those participating in the
driving performance sub-study were rated...as exhibiting
moderate or major difficulties, all drivers rated themselves
as being average to above average drivers...Thus, objective
evidence of driving ability... did not appear to impact on a
person's confidence or self-rating of abilities..."
Conclusions:
The "elderly driver problem" is overstated: as a group,
have fewer accidents and commit fewer violations than
younger drivers (Evans 1988).
Age per se is a poor indicator of driving performance
(Hakamies-Blomqvist 1996).
Bimodal distribution: elderly drivers are a mix of
healthy/safe and unhealthy/unsafe drivers.
Some evidence that elderly drivers are more at risk of an
accident at intersections.
Restricted UFOV and dementia are health problems that
particularly increase risk of an accident.
Conclusions:
Problem of reliably discriminating between safe and
unsafe elderly drivers: large-scale screening is unreliable
and not cost-effective.
Growing problem in all developed countries, as drivers
live longer and are less prepared to quit driving.
Sivak et al (1995): 1995, 1 in 7 U.S. drivers were 65+.
2030: will be 1 in 5.
Retchin and Arapolle (1993): by 2020, will be 33 million
U.S. drivers aged 65+.