The Victorian government will combat this by introducing strict new measures to ensure motorists can expect faster and smoother travel through Victorian roads.

From September 1, the Traffic Management Code of Practice will come into force, placing stricter rules on VicRoads and road work contractors.

It comes after reports reduced speed zones were often left in place too long, either throughout the night or when roadwork had ceased.

Roads and Ports Minister Tim Pallas said drivers were often frustrated and the new rules would alleviate that.

"We understand the frustration of motorists driving through road work zones when there is no work going on, which is why we're introducing the code of practice," he said.

The new code outlines that only in exceptional circumstances will road work speed limits be set at more than 20km/h below the normal posted limit.

It also places greater emphasis on the importance of VicRoads surveillance of speed zones and if contractors fail to meet the standards, they will be excluded from bidding for future projects.

VicRoads executive director Steve Brown said contractors would be closely monitored.

"VicRoads is making sure contractors play their part to minimise delays and driver frustration at road work sites where signed speed limits don't reflect the road environment," he said.

He said the Western Highway duplication in particular was a key area of interest that would be closely monitored.