Visible customized markings and adornments could be anything like bumper stickers, personalized license plates, window decals, air fresheners, religious figurines, and fuzzy dice.

They found that personalized markings on and inside cars are a better predictor for road rage than any other indicator. [Author's note: Although the study was performed in the United States, it is likely the conclusions are very much valid all over the world.]

Szlemdo, from the CSU Department of Psychology, states, "The number of territory markers predicted road rage better than vehicle value, condition or any of the things that we normally associate with aggressive driving. What's more, only the number of bumper stickers, and not their content, predicted road rage." [Auto Week: “Sticker shock: Bumper clutter may be a road rage warning"]

In other words, bumper stickers with passive messages such as “I’d Rather by Flying” and “Honk if You Love Jesus” could mean a potential road rage driver just as much as more aggressive ones such as “Stop Reading This Bumper Stick and Watch The Road” and “If You Can Read this Bumper Sticker, You’re Driving Too Close.”

Thus, people who customize their vehicles with such territorial markers are more likely to have road rage than other drivers.

In fact, the Szlemko team wrote in the article, "The more markers a car has, the more aggressively the person tends to drive when provoked.”

The article by the Szlemko team “Territorial Markings as a Predictor of Driver Aggression and Road Rage” was published in the Journal of Applied Social Psychology (38, 1664-1688 (2008).

The members of the research study are William J. Szlemko, Jacob A. Benfield, Paul A. Bell, Jerry L. Deffenbacher, and Luby Troup.

I find the word "territorial markings" very interesting in the paper's title. Please read on for more about this description.