Simple overtake ends in disaster on Sydney highway

An inattentive driver's disastrous lane change has shown why a quick glance in the side mirror isn't always enough for a smooth overtake.

A truckie driving along the M7 in Sydney's west has shared a video that shows a careless driver seemingly changing lanes without looking with calamitous results.

A video taken from a camera mounted on the roof of the truck shows the driver cruising along in the right lane of the two-lane highway with a sedan driving alongside.

Without warning, the sedan begins to switch lanes but doesn't get far before hitting the side of the truck and spinning out in front.

With no time to react the truck maintains its course as the car is shunted off the highway and crashes through a fence.

The driver lets out a stream of expletives as he pulls up a short distance up the road.

"Luckily he (the sedan driver) was ok," a the comment on the video shared overnight on Dash Cam Owners Australia Facebook page says.

"But he still tried to blame me for insurance purposes. Cameras don't lie old mate."

Comments on the video, filmed late last year and uploaded yesterday, were critical of the sedan driver, adding that there was nothing the truckie could do to avoid the crash.

"Shame this truck didn't obliterate the car and the driver so we'd have one less dishonest scumbag on our roads," one Facebook user said.