1. School of Civil Engineering
Highway Traffic and Safety Analyses
Lecture 26: Human Behavior and Road Safety
Purdue University
School of Civil Engineering
West Lafayette

2. Human Behavior
85-95 percent of crashes are attributed by experts to faulty human behavior

3. Human Behavior Theories Behavioral issues Countermeasures
Perceived vs. accepted risks
Theory of rational choice
Homeostasis theory
Behavioral issues
Aggressive driving
Runs on red
Speeding
Road rage
Countermeasures

4. Theories

5. Perceived vs. Accepted Risks
Perceived risk
Traffic and road situation
Driver traits
Driver experience (knowledge)
Driver state
Accepted risk
Driver state and traits
Travel purpose and time constraints
Perceived gain from taking a risk

6. Perceived and Accepted Risks versus Objective Risk
Road
Traffic
Driver
Objective Risk

7. Perceived and Accepted Risks versus Objective Risk
Road
Driver Behavior
Traffic
Driver
Objective Risk

8. Perceived and Accepted Risks versus Objective Risk
Perceived Risk
Road
Driver Behavior
Accepted
Risk
Traffic
Driver
Objective Risk

9. Perceived and Accepted Risks versus Objective Risk
Sweden changed to driving on the right. It resulted in 17% less road deaths in the first year (Guardian, 26 January 1996).
Accepted risk  , perceived risk 
=> Risk-taking behavior 
After introducing free-market economy in Poland in late 1980s, the crash rates increased by 30 percent.
Accepted risk , perceived risk 
=> Risk-taking behavior 

10. Theory of Rational Choice
Drivers consider
Alternative behaviors (slow down, accelerate, change lane, etc.)
costs associated with each behavior (likelihood of crash and its outcome)
benefits associated with each behavior (time gain, personal satisfaction)
Drivers select the alternative with the highest net benefit

11. Risk Homeostasis Drivers have their own target risk
They reduce (compensate) risk with more cautious behavior if
Perceived Risk > Target Risk
They change behavior towards more dangerous if
Perceived Risk < Target Risk

12. Risk Homeostasis Examples of risk-taking behavior The first indicator
Risky leisure activities (mountain climbing, rodeo riding, gambling, etc.)
The first indicator
In 1968, Congress mandated seat belts and several other safety equipment
20-percent reduction in fatalities were predicted as a result of improving millions of cars
Safety researches found no difference in fatalities

13. Risk Homeostasis Seat belts Speed limit
Volunteers drove go-karts with and without seat belts
The average speed of people wearing seat belts was higher than those who did not
Speed limit
In 1987, the federal government allowed for raising speed limit from 55 to 65 miles/hour
Fatalities in states with the 65 speed limit where lower than in the other states by three percent
WATCH: Do Safer Cars = Dangerous Drivers?

14. Behavioral Issues

15. Percent of Respondents
Aggressive Driving What behavior is aggressive? – survey of Canadian drivers
Percent of Respondents
Behavior
1999
2000
Tailgating 93
Passing on the shoulder 88 87
Making rude gestures 86
Pulling into someone else's parking space 80 82
Changing lanes without signaling 75 73
Flashing high beams at car in front 74 72
Drive through yellow lights turning red 69
Merge at last second with traffic on highway 66
Speeding (20km/h or more over speed limit) 65

16. Aggressive Driving Red Signal Running
In 1998, there were 89,000 red light running crashes that resulted in 80,000 injuries and 986 deaths.
56 percent of Americans admit to running red lights.

17. Aggressive Driving Red Signal Running
Indiana drivers’ survey (2000/2001)
56 % see red signal running several times a week
55 % think that drivers are in hurry
27 % think that drivers do not pay attention
68 % think that less than 10% violators are ticketed by the police
59 % believe in enforcement
78 % would support photo-enforcement

18. Aggressive Driving Red Signal Running
West Lafayette research (2001/2002)
No enforcement: 20 % of drivers arriving at the beginning of red signal runs it
Residual effect of police enforcement: 5 % of drivers arriving at the beginning of red signal runs it
The residual effect does not last long
Violation rate significantly lower if students aren’t in the flow (vacation)

19. Aggressive Driving Speeding

20. Aggressive Driving Speeding

21. Cultural norms of disrespect = Road Rage
More congestion +
Cultural norms of disrespect =
Road Rage

22. Road Rage Verbal Quiet Epic yelling, honking, rude gestures, insulting
rushing, competing, resisting
Epic
cutting in, blocking, chasing, fighting, shooting

23. Countermeasures

24. Countermeasures Perceived vs. Accepted Risks
Increase the risk perception
Educate about human limitations
Provide road hazard facts to public
Educate about drug impacts
Display warning signs
Law and enforcement (additional risk)
Decrease the risk acceptance
Gratification of safe driving (premium by employer)
Any other ideas?

25. Countermeasures Aggressive Driving – AAA Survey of Agencies http://www

26. Countermeasures Red Signal Running http://safety. fhwa. dot
Photo-enforcement
1997, Oxnard, California, population 151,000
Nine camera sites, $104 fine and one point on the driver's license.
A 30-day warning period during which red light cameras photographed violators, but no tickets were issued.
The red light violation rate reduced 42 percent.
Increase of red signal compliance on unequipped intersections as well

27. Countermeasures Speeding –Survey of Drivers http://www. nhtsa. dot
More police assigned to traffic (85%)
More frequent ticketing (82%)
Double or triple fines (81%)
Revoking licenses more often (81%)
Increased insurance costs (80%)
Road design changes (78%)

28. Countermeasures Road Rage webpages.marshall.edu/~harrison2
Database of Unsafe Driving – license plate numbers of drivers who were acting upon road rage
Quality Driving Circles – groups of drivers who meet discuss their difficult driving experience
Education - educational materials, public service announcements, self-tests, self-help and self-education through the Internet

29. Countermeasures Road Rage http://www. aaafts
Legislation directed at controlling road rage in 17 states
Enforcement: unmarked cars, plain-clothes police officers, helicopters, airplanes, video cameras, air patrols in contact with grounded policemen (TRIAD – Targeting Reckless, Intimidating, and Aggressive Driving in Ohio)

30. Countermeasures Improve the Road www.nous.org.uk/reform.html
"Don't attempt to reform man. An adequately organized environment will permit humanity's original, innate capabilities to become successful. Politics and conventionalized education have sought erroneously to mould or reform humanity.“
Utopia or Oblivion, Buckminster Fuller, 1969.
"increasing safety and decreasing accidents by engineering improvements of motor vehicles while also providing overpasses and banked turns for the vehicles to drive on, instead of trying to reform the vehicle-drivers' behaviors" .
Critical Path, Buckminster Fuller, 1981.