Traffic banked up for kilometres after eight cars and truck crash on Sydney's M4

A truck has been involved in a crash with eight cars on the M4 in Sydney's west. 

Eighteen people have been assessed by paramedics and a man freed after spending more than an hour trapped in his van in Prospect at the Light Horse interchange.

Luckily, no one is believed to have suffered significant injuries. 

The crash happened at 4.40pm, just as many started heading home on their evening commutes, with more than 11km of traffic now at a standstill.

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All westbound lanes of the M4 are closed and traffic is being diverted at the Reservoir Road off-ramp.

Motorists are being urged to use the Great Western Highway instead.

Eastbound lanes have reopened but traffic is also heavy in that direction and there are queues banked up more than 5km from Eastern Creek.

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Source: 9News