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 40-49 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.

Poor definitions of "elderly":

e.g. Shanmugaratnam et al (2010): average age of "elderly" group = 65, but ranged from 44 to 82 !

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 risk of 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 age-group.

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 age-group 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 self-performed 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 with other road users

Predict other's behaviour and behave predictably.

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..."

Freund et al (2005):

47 elderly drivers referred for testing. 38% were found to be unsafe; all of these rated their expected simulator driving performance to be the same or better than other drivers of their age.

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:

Shanmugaratnam et al (2010): elderly drivers' overall performance is a mixture of beneficial effects of judgement (drive slower, avoid difficult conditions) and adverse effects of impaired ability (cognitive and psychomotor slowing).

Problem of reliably discriminating between safe and unsafe elderly drivers: large-scale screening is unreliable and not cost-effective.

A 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+.