A shocking crash on one of Sydney‘s busiest roads left two cars flipped on their sides and traffic backed up for kilometres.

Shortly before 2.30pm a car and small truck collided westbound on the M4 motorway at Eastern Creek.

Shocked motorists came to the aid of the people in the two vehicles with police telling Daily Mail all walked away unscathed but were left ‘shaken’ by the incident.

Police also said speeding or alcohol were not a factor in the accident.  

Two of the three lanes were closed but one reopened just after 3pm.

The off ramp from the M4 to the M7 was still closed at 3.30pm as fire crews cleaned up a fuel spill.

Motorists have been warned to avoid the area as traffic is slow between the M7 and Prospect Highway.