Older drivers and their accidents

1
Older drivers and their accidents
Dr Dianne Parker Driver Behaviour Research
Unit Department of Psychology University of
Manchester Funder Department of Environment,
Transport and the Regions, 36 months
2
Why study the older driver?

• proportion of older people who drive is
  increasing (Joint, 1995)
• social change (social mobility, out of town
  shopping/leisure) means maintaining personal
  mobility is crucial to quality of life (Owsley,
  1997)
• older drivers need to know their areas of likely
  strength and weakness

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The older driver project

• Phase One the Ageing Driver Questionnaire
• Surveyed 1,993 drivers aged 49-90
• Phase Two the laboratory tests
• 550 drivers over three 1.5 hour sessions
• Phase Three the on-road assessments
• 200 drivers, two routes, two different ADIs

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The Manchester DBQ 1

• How often, if at all, do you do each of the
  following?
• 0 never
• 1 hardly ever
• 2 occasionally
• 3 quite often
• 4 frequently
• 5 nearly all the time

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The Manchester DBQ 2

• Top two errors
• Underestimate speed of an oncoming vehicle when
• overtaking (1.70)
• Brake too quickly, or steer wrong way into a
  skid (1.51)
• Top two violations
• Disregard speed limits (2.17)
• Cross a junction as the lights turn against you
  (1.50)
• Top two lapses
• Misread signs and take wrong turn off a
  roundabout (2.40)
• Get into wrong lane approaching a
  roundabout/junction (2.25)

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Factors emerging

• The lapse and error factors emerged virtually as
  expected
• Violations split into two types
• Interpersonally aggressive violations plus close
  following
• Ordinary violations
• A new factor (factor 5)
• One lapse - driving away in 3rd
• One violation - Cross traffic lights turning red

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Predicting active accidents
Wald Odds ratio Age
1.76 1.00 Mileage 15.86 1.00 Gender 2.99 1
.24 Errors 11.30 1.87 Lapses 13.91 1.70
Viols.1 0.38 0.90 Viols.2
2.98 1.22 Factor 5 0.55 1.10
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Predicting passive accidents
Wald Odds ratio Age
1.42 0.99 Mileage 1.98 1.00 Gender
0.59 0.91 Errors 0.18 0.92 Lapses
9.09 1.54 Viols.1 3.95 1.41 Viols.2
0.77 0.90 Factor 5 0.14 0.95
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Are those who have active accidents different?
Accident No Sig diff? accident Errors
1.51 1.37 Lapses 2.18 2.00 Viols.1 1.2
4 1.19 ns Viols.2 1.71 1.59 Factor
5 1.54 1.42
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Are those who have passive accidents different?
Accident No Sig diff? accident Errors
1.42 1.40 ns Lapses 2.11 2.03 Viols.1 1.24
1.19 Viols.2 1.65 1.61 ns Factor
5 1.47 1.45 ns
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Are older drivers different?

• Yes, they report more lapses than other drivers.
  Why?
• These seem to occur in situations where they
  need to
• do several things at once
• Then, cognitive demands may exceed capacity
• If something has to fail, the task aspects least
  
• safety-critical should be the one to go
• Such aspects include those revealed as lapses

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Why do lapses predict accidents?

• Most lapses seem relatively harmless
• However they may reflect a generally inattentive
  and/or
• hesitant driving style
• The behaviour on the road of the lapse-prone
  driver
• may be unpredictable
• They may fail to pick up on other drivers
  departures
• from the ordinary

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Conclusions

• Among the over 50s, a lapse-prone driving style
  is
• linked with accident involvement, even after
  the effects
• of age, gender and mileage have been taken
  into account
• Road safety interventions targeted at older
  drivers
• should focus on maintaining and/or supporting
  the
• complex skills necessary for driving
• A self-administered diagnostic test (DBQ?) would
  be a
• useful first step