First, they attempted to define aggressive driving. After examing working-definitions put forth by among others the National Highway Transportation Safety Administration and the Transportation Research Board, AAA suggests the following: "any unsafe driving behavior, performed deliberately and with ill intention or disregard for safety, can constitute aggressive driving".
The study then goes on to reference specific driving behaviors including driving too fast for conditions, following too closely, failure to yield right of way, passing where prohibited and failure to obey traffic signals, signs and road markings.
These behaviors are ones specifically assigned codes in the FARS or Fatality Analysis Reporting System discussed with some frequency on this website. AAA's findings were that more than 56% of fatal accidents involved at least one element of aggressive driving.
The paper goes on to point out a dichotomy that might lie at the heart of the problem. 78% of Americans regard aggressive driving as a serious or extremely serious traffic safety problem yet large numbers of the same respondants admit to engaging in essentially aggressive driving.
AAA tries to focus drivers on how important it is to realize the extent to which aggressive driving on the part of one driver may lead to responsive dangerous driving from others. For more go to: http://www.aaafoundation.org/pdf/AggressiveDrivingResearchUpdate2009.pdf