Signs warning motorists of a road hazard have been erected along the northbound lanes of the freeway near Gisborne South and the speed limit has been reduced to 80kmh.

VicRoads regional director Mal Kersting said: "Over the recent summer period, some road surface 'bleeding' has occurred on several sections of the northbound lanes, whereby excess bitumen rises to the surface.

"This can lead to reduced road grip, which can result in the road being slippery in wet conditions."

Mr Kersting said VicRoads contractors were arranging repairs.

Last month, there were several incidents on both sides of the freeway.

*On February 21, a semi-trailer loaded with paper rolled and was destroyed by a fire and the freeway near Gisborne South was shut for more than eight hours.

*On February 13, three Sunbury CFA volunteers were injured when their tanker rolled. They were going to another truck rollover northbound on the freeway near Gisborne.

The two accidents were about a kilometre apart. Another car travelling north rolled on the freeway during heavy rain on February 10.

*Last Wednesday, a car and a caravan travelling south rolled about 8pm.

The driver was taken to hospital with head injuries. The passenger was not hurt.

Sergeant Geoff Neil, officer in charge of Gisborne's traffic management unit, said people needed to comply with speed restrictions.

"Given the amount of incidents of vehicles running off the road within that two-kilometre stretch, there is obviously an issue there. I think it's great VicRoads have acknowledged that and are taking steps to make the road safer for all users."

*Police impounded a car on the freeway near Macedon last Wednesday.

It was recorded travelling south at speeds exceeding 160kmh.

The 45-year-old male driver has been charged on summons.