Cornell University Ergonomics Web

DEA 3250/6510 CLASS NOTES

The Automobile as a Complex System

About 50.000 people are killed annually in the United States in car accidents. This is more than the total of those Americans killed in the Vietnam war, and more than twice as many as people who die from tobacco-related illnesses. No one has documented specifically how many have died from asbestos-related lung disease, but the magnitude of the risk is trivial compared to auto accidents. The auto can be a lethal product.


AUTO SYSTEM

Vehicle Subsystem
Engine design
safety - seatbelts, airbags
security - stopping car from being stolen a transmitter is imbedded into the body of the vehicle for tracking (downside is the loss of privacy)

Vehicle Service Subsystems
fueling - electric vehicles but today take too long to recharge. The problem is that the batteries aren't designed for rapid charging or easy swapping
repairs
recovery

Traffic Control Subsystems
regulations
road signs
traffic information
- satellite systems built in to car
- Seiko - watch that downloads info from satellite

Road System
Planning and Engineering
- interchanges
ex. can reduce driver fatigue by having more rest stops
- overpasses
- visibility
- maintainability
ex. of pavement, sound of vehicle is important cue to how you drive
- snow & ice control
ex. New Jersey is bad for snow coverage and has a higher accident rate

Personnel Subsytem
driver skills training , characteristics
- simulation systems
- can bring people to a relatively high experience level
- can simulate unusual and hazardous conditions

Driver Displays - what information is displayed? In what ways is it displayed? 80% of information is vision-based
ex. It's possible to fit someone with an eye-tracking head set that they would wear when driving a car.

What are Visual Scan Patterns?

1. Unfamiliarity
- We make more eye movements and scan more thoroughly on unfamiliar routes.
- On more familiar ones we may be more likely to have an accident

2. Novices vs Experts
- Novices focus eye movements on a much smaller area, "perceptual tunneling" therefore are less likely to see peripheral activity (e.g. a child with a run away ball)
-How long does it take to build up experience?

3. Follow other vehicles
- We tend to focus on center of the road behind vehicles. The car acts as a focal object.
- People get lost more in heavy traffic.

4. Temporary impairment issues
- driver fatigue - focus more on perceptual tunneling

Perception of vehicle speed

a) restricted hearing, underestimation of speed (for example from ear muffs)
- implications for pavement design
- as cars become more aerodynamic, people underestimate speed more
- ex. the difference between riding in a convertible or enclosed car

b) adaptation - comes with continuous high speed motion results in adaptation that results in under estimation of speed

c) rate of closure and perception of spacing, being able to judge how quickly you're approaching another vehicle Judgements appear to bebetter at high speed than low speed. Ability to judge how far away you are from another car (e.g. people in small cares drive closer to other cars
- important dimension is the amount of road surface visible to the driver (e.g. use of chevrons on road surface help judge spacing of cars)

Reaction Times and Driver Characteristics
60% of all accidents are from driver error, not performance.
- speed of decision
- speed of recognition both contribute to error
ex. speed of braking
US average reaction time - 2.5 seconds
For most reaction times, nothing is done the first second!

Personal Variables

Age
-- For men -- "attentional" differences as the brain continues to develop into the 20's
-- hormonal changes still occurring
Sex 

-- after age 40 sex effect is fairly irrelevant
-- 15-45 years, old sex is a relevant factor
-- women have a 70% higher chance of being injured
-- women have a 25% higher chance of being killed
-- differences in stress - blood pressure doesn't get back to normal
-- differences in where information is processed until 10 p.m.,
--women's into both hemispheres, men just the left side

Temporary Impairment
Alcohol - Toxic to liver and nervous system, acts as a depressant that inhibits nerve function, slows reaction time, disrupts neuromuscular control etc.

Blood Alcohol Content (BAC) - The mass of alcohol X 100 mass of blood
(e.g. 1 part alcohol/ 1000 parts blood 1/1000 X 100 = 0.1%)

In Canada & Britain the level is 0.08%

BAC Accident rate

Blood alcohol  Accident rate
 No alcohol  1
 .001 - .049  .88
 .050- .099   1.98
 .01 - .149  10.1
 .150 - .199  31.9
 >.2  40.9

If you eat things high in fructose to helps break down alcohol more quickly.

Stress
When fatigued, tired, performance suffers, likewise when very nervous or anxious.
When driving, the heart rate goes up at intersections.
Train people to relax in emergency situations.


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