Victorian police blame human error, not the state's fixed speed cameras, for a fine wrongly issued to a bus driver on the Hume Highway near Melbourne.

The driver from Seymour Coaches, at Seymour, in central Victoria, was issued with the $250 fine after Victoria Police alleged he was detected doing 123km/h in a 110km/h zone on the Hume Freeway at Craigieburn, north of Melbourne, in April.

Buses are restricted to 100km/h on Victoria's roads, even in 110km/h zones.

Two years ago, 100 drivers were wrongly booked for speeding at Somerton, in Melbourne's north, because of an incorrectly set camera.

And in 2003, all fixed speed cameras on the Western Ring Road, CityLink tunnels and Monash Freeway were tested and fines suspended after readings on three units were deemed to be questionable.

Seymour Coaches managing director Peter Louchnan said it was not possible for the bus to do 123km/h because it was fitted with a speed limiter.

"The vehicle is speed limited to 100km/h from the factory," Mr Louchnan told Southern Cross Broadcasting.

"Once it hits that 100km/h on the speedometer the accelerator is flat (on the floor), it won't do any more."

Mr Louchnan said the speed limiter had not been tampered with and was regularly checked by government inspectors, the last time at Christmas.

But Victoria Police said human error was to blame, and not a fault with the camera.

"It is not a technical systems fault, it is an error in human verification," Superintendent Shane Patton said.

"My staff member here hasn't done their job properly, hasn't checked the images properly."

"It's totally unacceptable what has occurred."

Supt Patton said the bus had been photographed at four fixed speed camera check points on the freeway.

He said the error occurred because another bus from Seymour Coaches with a similar number plate was travelling in the same direction on that stretch of the freeway at the same time.

"On this occasion what has happened is that there are two different vehicles with virtually identical number plates from the same company.

"That should have been picked up by the verifier."

Victoria Police has now withdrawn the fine.

Seymour coaches said it was satisfied with the outcome, but the bus driver "Warren" said he had no faith in the speed camera system.

"There are lots of number plates out there that are similar," Warren said.

"What's going to happen? Are these people going to get booked and have to resort to taking it to court before something is done about it."

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