Having found that drivers who repeat traffic offences are likely to commit further violations, we investigated the significance of this fact.
Drivers who drive long distances or drive frequently are exposed to greater risk of meeting up with accidents, and are therefore likely to cause traffic mishaps. Here, however, we conducted the analysis focusing on the types and characteristics of traffic offences committed by the drivers.
When giving safety education to drivers who are repeatedly involved in auto accidents, it is important to focus on why that particular driver repeats accidents. To ascertain the cause of an accident it is necessary to look into the process that led to it.
Column: Poisson Distribution Clarifies Traffic Offenses
Have you ever heard of a Poisson distribution? A number of events are assumed to follow this distribution when they have been observed for long enough, and if:
1)the events occur randomly,
2)the events do not occur often, and
3)the events do not repeat one after another (they are independent)
There are many events that follow such a distribution in our daily life: the number of phone calls that one receives, the number of people waiting for a taxi or in supermarket checkout lines,the frequency of stopping in gas stations, and the number of traffic accidents.
Let us assume that the number of traffic violations also follows the Poisson distribution.
The chart below shows the number of traffic offences according to the type of violation experienced by drivers.
Dotted lines in the chart indicate the number of offenders there would be if they followed the Poisson distribution, whereas solid lines represent the actual number of drivers who committed those violations.
As can be readily seen, the actual numbers begin to deviate from the Poisson distribution line at around the point where there are three-time offenders. From these results, it can be concluded that the number of traffic offenders does not follow the Poisson distribution. Furthermore, the specific characteristics of the traffic violations become apparent from three-time offenders onward.
Repeating parking violations, speeding, or non-use of seatbelts three times or more is apparently not accidental but rather reflects the character traits of the driver. Some traffic offences are indeed due to coincidence, but most of them occur due to factors that are more than mere chance.
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