Road rage in drivers is often visibly expressed through such actions as honking of the horn, tailgating, aggressive and dangerous driving habits, and other unsafe motorist activities.

The abstract goes on to say, “Aggressive driving may occur when social norms for defending a primary territory (i.e., one's automobile) become confused with less aggressive norms for defending a public territory (i.e., the road).”

And, “Both number of territory markers (e.g., bumper stickers, decals) and attachment to the vehicle were significant predictors of aggressive driving. Mere presence of a territory marker predicts increased use of the vehicle to express anger and decreased use of adaptive/constructive expressions.”

The article explains the association of personal car markings and road rage as a way by those drivers to protect their territory. They are being “territorial”; thus, stating this is “my street” and “my lanes.”

Many scientific tudies in the past have shown that animals--including humans,--become more territorial when in more crowded conditions.

According to the Nature article “Bumper stickers reveal link to road rage,” the number of road rage incidents have been increasing. In 1995, the American Automobile Association (AAA) reported 200 deaths and 12,000 injuries linked to road rage.

In 2009, those numbers increased to 370 deaths and over 25,000 injuries. The AAA states, however, that many more road rage incidents go unreported when injuries and deaths are not involved.

The research team asked hundreds of drivers numerous questions concerning their vehicles and driving habits. Vehicle questions included such things as its condition (new, used, old), type (make and model), and estimated value (in dollars).

Whether they have personalized the vehicle in any way was another question. Such things as special painting and detailing, larger stereo systems, and other various customized work were considered ways to personalize the vehicle. Other more minor additions such as bumper stickers, dash toys and figurines, and seat covers are also considered personal additions.

The drivers were also asked about their driving habits and how they would respond to various driving conditions and situations.

A pre-existing scale, which they called “Use of vehicle to express anger,” was used to analyze the answers. For instance, the scale would have been used in interpreting the answer to the question “If someone is driving slow in the fast lane, how angry does this make you?”

The researchers also stated they included “decoy” questions so participants would not realize they were being tested for aggressiveness on the roadways. For instance, “What kind of music do you listen to while driving?”

What specifically did the researchers conclude on personalized items on cars and and the likelihood of road rage? Please read on.