How safety measures can change drivers' behavior
By: Drivers.com staff
Date: Friday, 23. March 2007
This is a summary of an article by Stein Fosser, Fridulv
Sagberg, and Inger Anne F. StŠtermo, titled "Behavioral
adaptation to airbags and antilock brakes", which was published
in Nordic Road & Transport Research, No. 3,
Measures to improve safety don't always have the intended
effect. Sometimes measures such as driving skills programs,
antilock braking systems, airbags, enforcement programs produce
changes in behavior that reduce the effects of the measures or
counteract them entirely.
The behavior adaptation that follows such measures is often
termed "risk compensation" and it can partly or completely offset
the intended safety effects of measures. Studded tires, for
example, give better traction on slippery surfaces, but they have
been shown to be associated with increased driving speeds. It's
likely that they also result in increased exposure to risk, since
drivers may venture forth in conditions that would deter them from
driving if they were not equipped with studded tires.
A study conducted by the Norwegian Institute of Transport
Economics looked at behavioral adaptation to antilock braking
systems (ABS) and airbags. The hypothesis was that
accident-reducing measures such as ABS are compensated to a larger
extent than injury-reducing measures such as airbags.
It seemed less likely that the injury-reducing measure (such as
an airbag) would result in an increased risk of accident. A measure
that reduces the risk of an accident, on the other hand, seems more
likely to result in behavior that would tend to maintain accident
An important factor is whether the individual is aware of the
safety measure. Even more important is whether the measure produces
feedback. For example, in the case of airbags the device produces
no feedback whatsoever (except in the rare case of an accident).
ABS, on the other hand, may give feedback on slippery roads in
terms of steering performance and braking. This may give drivers a
feeling of extra security.
Risk compensation may also be manifested in strategic driving
decisions such as whether or not to make a trip or decisions about
when and where to drive. It may also result in reduced use of
safety equipment, for instance if airbags result in seat belts not
The Oslo taxi driver study
In May, 1995, researchers from the Institute of Transport
Economics studied the behavior of taxi drivers driving from Oslo
city to the airport on a stretch of the E18 motorway.
Taxi drivers were chosen because this made it easier to randomly
select a group. The possibility of individuals "self selecting" for
the study was eliminated. In addition, since many taxi drivers
don't own the taxi they are driving and are assigned to a vehicle
rather than choosing it, the possibility that the presence or
absence or ABS would be due to driver preference or personality was
avoided. This insured that the equipment of the taxis was
independent of driver characteristics.
By choosing the motorway from the city to the airport
researchers were able to track the taxis to their destination and
then use a questionnaire to get information about whether the cars
were equipped with airbags or ABS.
The data basis for the behavioral measurements consisted of
video-recordings of traffic on a straight 180-metre road section.
Driver behavior was recorded for 1,384 different taxis looking at
driving features such as speed, headway, lane changes, lane
occupancy, and the variability of lateral position.
Behavioral data from observation was matched with information
from questionnaires administered when the taxis arrived at their
airport destination. Drivers reported personal background
information and answered questions about driving behavior. The
questionnaire was completed by 517 drivers. Some analyses were
based on the whole sample of drivers with questionnaire data, while
the main analyses included only those cars for which a match was
possible between questionnaire and driving data.
Drivers of taxis with both airbags and ABS reported less
opportunity to drive as fast as they wanted to, compared with
drivers who didn't have these equipments. In other words, there was
a tendency for behavioral adaptation.
Separate comparisons for ABS and airbags showed that this
difference was significant only for airbags. The tendency was not
reflected in higher speeds, probably because the density of traffic
prevented drivers from choosing speed at their own discretion.
Taxis with ABS had significantly shorter time headways than
taxis without ABS. Simple comparisons showed a lower rate of seat
belt use among drivers with ABS and fewer lane changes. However,
multiple regression analysis indicated that the lower seat belt use
might be explained by driver background factors or by car
characteristics other than ABS or airbags.
The results of the study were unclear on the question of whether
accident-reducing measures (such as ABS) might have a greater
effect than injury-reducing ones (such as airbags). The headway
results support the hypothesis, but self-reported data suggest
possible compensation also for airbags.
More weight can be placed on the behavioral results since the
self-reported data may be questioned on general methodological
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The moron coming torawds you dont drink and happy driving.The speed limitjust drive according to road conditions expect the unexpected from other driversyou may be good driver but you dont know what the unexpected from other driversyou may be likesafe journeys and happy driving.
great any body doing research on driver behavior like me?