Too many speed zones are confusing WA motorists and causing them to be fined unreasonably, Colin Barnett says.

The Premier said yesterday he wanted speed limits rationalised, which Transport Minister Dean Nalder was looking at after Victorian moves to gradually phase out 70km/h and 90km/h zones.

The Opposition complained the Government had been talking about the issue for years and urged it to make a decision.

A Victorian Government speed limit review in 2011-12 attracted 600 public submissions regarding confusing speed limit signs, including Carlisle Street in Balaclava, Melbourne, which had 11 limits in 4.8km.

It no longer prescribes 70km/h and 90km/h zones and will phase them out, and has removed 80km/h "buffer zones" gradually reducing speeds of vehicles approaching towns in country areas.

Mr Barnett said he thought phasing out 70km/h and 90km/h zones was a good idea.

"From my own experience, I frequently drive to Toodyay and the speed limit just changes continuously, so I think less categories of speed limit and simplifying it is a good measure," he said.

"There are too many different speed zones and it can confuse motorists and they can unreasonably get caught for minor transgressions in speeding - not because they are driving in an irresponsible way but simply the zone has changed and they haven't noticed it."

Mr Nalder's parliamentary secretary Jim Chown told Parliament this week that Main Roads was concerned removing buffer zones would result in big variations in vehicle speeds.

But the authority believed reducing speed limits would benefit motorists and it would monitor Victorian reforms.

Shadow transport minister Ken Travers said any changes should be done only on the advice of road safety experts but he supported the issue being looked at.

"Victoria prides itself on being a leader in road safety," Mr Travers said. "If we need public consultation then let's do it, but I can't see how its taken three years for the Government to decide to do a review."