Behaviour a big factor

Mohammed Adam makes a valid point in his column about the behaviour of individual drivers being a substantial factor in vehicle collisions, with or without snow tires in winter. Unfortunately, the official statistics he cites don’t support the case. Adam contends that they show little significant difference between the percentage of vehicle collisions in Ontario in “wintry” or “summery” months. However, the comparison that should be made is between total kilometres driven in those months and the percentage of vehicle collisions then.

There is ample evidence that the number of vehicle collisions vary directly with miles driven and speed. These are “dependant variables” and any meaningful comparison of the rate of vehicle collisions has to first “normalize” the statistics.

However, Adam touches on another relevant point with his remarks about SUV drivers thinking they are “bulletproof in their four-wheel drives.” This is a well-researched phenomenon in human behaviour known as “risk homeostasis.” In effect, this means that people tend to adjust their actions to conform to a level of risk which is (subconsciously) acceptable to them. More than a decade ago, Germany mandated anti-lock braking for taxis, figuring that with an improved safe stopping distance, there would be fewer collisions. Indeed the accident rate for taxis did initially drop. But it shortly went back up to the previous level. Subsequent research showed that many taxi drivers were simply driving even closer to other vehicles than before and had accepted the same level of risk of collisions as before the antilock braking was introduced. The same thing happened when the maximum speed limit on U.S. Interstate highways was temporarily reduced to 55 mph.

Put winter tires on a four-wheeldrive SUV and who knows what risk adjustment the drivers will make. It is indeed about behaviour as much as tire tread.

PETER CALAMAI, Adjunct Research Professor, School of Journalism and Communication, Carleton University, Ottawa