From: http://www.dmv.state.va.us/webdoc/general/safety/aggressive/definition.asp DMV Safety: Aggressive Driving: Definitions and Facts Aggressive driving is a combination of unsafe and unlawful driving actions that show a conscious and willful disregard for safety. What causes aggressive driving? -Crowded roads -Being in a hurry -Road work -Stress from other areas of life -Dangerous driving attitudes (NHTSA) Aggressive driving behaviors include: -Failing to yield the right of way -Following too closely -Unsafe lane changes -Improper passing -Speeding -Disobeying traffic signals and signs -Reckless driving Individuals who exhibit aggressive driving behaviors cross all age, race, socioeconomic, and gender lines. Even drivers who are usually mild-mannered can "blow their top" behind the wheel. (Network of Employers for Traffic Safety) Speeding is one of the most common offenses committed by aggressive drivers. (NHTSA) Aggressive driving can escalate into road rage--a criminal offense. Road rage is an assault with a motor vehicle or other dangerous weapon by the operator or passenger(s) of one motor vehicle on the operator or passenger(s) of another motor vehicle. Road rage is caused by an incident that occurred on a roadway. (NHTSA) Even though the material quoted here is from the DMV, Virginia, USA, it is applicable in most places. The only thing that appears to be missing, but is mentioned on other sites is gesturing at other motorists as a behavior of aggressive driving. I believe it is part of the aggressive behavior, but I can see that it does not meet the definition of aggressive driving. Think about it though, how many times have you seen a situation similar to this: Driver A cuts off Driver B, Driver B responds by flipping off Driver A. Driver A becomes enraged by the gesture and flips the bird back. This typically ends with the two drivers continuing to enrage each other as they go along (usually by doing things that do fall under the defined "aggressive driving"). Sad, very sad and realy not worth the danger they put themselves and others in. Hope this answer helped :)

Practically speaking, in a perfect world, the purpose of driving would be to get from place to place safely while courteously sharing the road. Vehicles would be strictly utilitarian, like the original VW Beetle, with no fancy features and barely enough power to get from zero to sixty in 15 minutes. Few drivers, however, seem to understand the true purpose of driving. Those who do are the overly cautious slowpokes who frustrate the typical driver. For many motorists, driving is a form of self-expression. Behind the wheel you become the free-wheeling, devil-may-care, risk-taker you really are. Driving too fast is unsafe, sure, but it's cool. You want to show the world you're not a wimp, not one of those cowardly courteous drivers. For some, it is a chance to compensate for all the slights and humiliations they suffer in daily life. On the road, these drivers take a back seat to no one (by God!). The road is their personal race track. They bristle at having to share the road. Drivers who don't conform to their swashbuckling style will feel their wrath. For them the purpose of driving is to get from place to place as fast as possible in a display of awesome driving skill. This involves weaving through traffic like a stunt driver, cutting between cars with only inches to spare, tailgating those who won't get out of the way, deftly cutting off other racers, and generally posing a menace. Some will go so far as to carry a gun in the car and blast anyone who gives them grief.

Aggresive drivers are a product of modern day society. agg. drivers are generally not born, they become aggresive for many reasons, too numerous to mention. drugs and alcohol play a big part. also, people not taking their medication or taking illegal medications. domestic violence plays a big part, with drivers taking out their domestic problems on the road against you and i. construction work definetely makes nerves grow weary. some people just cannot wait in line for anything. the increase number of autos on the road. defensive driving is a must against an aggresive driver. keep your cool and get out of their way. they may be armed or stoned, you never know. out on the interstate is not the place for a confrontation. it is going to get worse as the population grows. take a deep breath and tighten your seat belt. you could be in for a long ride. end

Impatient, stress, evil people.