Driver aggression on Australian roads is increasing, causing concern about the link to collisions.

The 15th annual AAMI crash index has found 91% of drivers believe drivers are becoming more aggressive, and more than half gesture rudely or yell and swear at other drivers.

The number of victims of road rage has increased - rude gestures (79%), verbal abuse (64%) and tailgating (65%) are the most common.

More alarming is that 29% of drivers have been followed, 12% forced off the road, 7% had their car wilfully damaged and 2% have been assaulted.

Nearly 90% of respondents blame driver aggression on traffic congestion, with the number of people taking 30 minutes or more to drive to work tripling since 2005.

Meanwhile, 84% of drivers admit to speeding, 33% have driven while over the legal alcohol limit and 21% have driven after taking prescription drugs that warn against operating a motor vehicle.