HORSHAM and Green Lake fire brigades are controlling a small fire on the Western Highway, about 10 kilometres south-east of Horsham.
The fire is thought to have been started by a trailer wheel bearing at 8pm.
A Narre Warren man, driving a black Holden, was towing the trailer towards Horsham.
His partner was driving behind him and noticed smoke coming from the trailer.
A witness said the trailer lit up when the man pulled over.
He said the fire burnt about a hectare along the side of the road.
No one was injured.
Police also attended and controlled traffic.