While police are praising the opening of the bypass, which has lifted some of the pressure from once-congested roads through Pakenham and Officer, they are disappointed that a number of motorists have not heeded the temporary speed limits.

Sergeant Chris Marlaw said police had received numerous calls from motorists reporting speeding cars.

"This is disappointing and, in our opinion, very selfish."

He said the bypass had been great for traffic flow along the Princes Highway in Pakenham and a reduced number of vehicles on this road would be safer for pedestrians, particularly students, crossing the road.

One motorist told the Journal that the bypass had cut her daily drive to and from work by more than 10 minutes.

"Once we can drive at full speed, it will make the trip a lot quicker. It is much better because there are no lights.

"But even if it does get busy, at least now we have an alternative route."

She said the only frustrating thing had been the number of motorists disobeying the speed limits, sending loose stones into the air.

Central Ward councillor Kate Lempriere said she was also amazed that VicRoads had used a "country road surface" on the road.

"It will be interesting to see if you get two or three 30- or 40-degree days out here, whether it will lift with all the B-doubles [trucks] which will be using the road.

"I just hope they haven't set themselves up to cost them more money in the future."

VicRoads did not return the Journal's call for comment.