The number of speed cameras could double on New Zealand roads, with $10m held in reserve for the delivery of more in the next three years.

The New Zealand Transport Agency had the money set aside, but was waiting on a business case from police, a spokesman said.

At present 55 speed cameras operated around the country, and a proposal for an increase was part of the road policing plan.

However, police had yet to decide whether more would be installed and how many.

"The Safer Journeys strategy indentified that the way forward for reducing road trauma is investing in technology, [including speed cameras]," a police spokesman said.

"But this is dependent on a cost benefit analysis showing clear benefit."

Associate Transport Minister Simon Bridges welcomed plans to increase the number of cameras, saying New Zealand was on the light side when compared to Australia.

Victoria and New South Wales has 4.8 and 2.5 speed cameras per 100,000 people respectively, while New Zealand only had 1.3, he said.

"All international evidence shows that speed cameras are highly effective in slowing vehicles down and saving lives."

Bridges said cameras could include a mix of fixed, mobile, and point to point cameras.

He didn't have a good sense of the cost, but informal advice showed 25 speed cameras could be bought for $4m, he said.

"I think it would be dangerous to say what that means in terms of $10 million. "The technology is always changing and getting better, so it's just what police decide they want and what numbers," he said.

AA motoring affairs general manager Mike Noon said the AA had worked with police on where the cameras could be placed earlier this year.

"The cameras are put in areas where there has been a history of speed-related crashes and injuries, or where we know that the speeds are well above what is safe."

"We're supportive of fixed cameras being placed in areas where we know there is a risk," he said.

Noon last year sparked debate on whether the cameras should be signed to give drivers the opportunity to check their speed and slow down.

"What we want here is not necessarily to write a lot of tickets, what we want is for motorists to understand and comply and keep the speed down in areas with speed-related risk," he said.

Chief executive of road safety charity Brake, Mary Williams, said the speed cameras would be money well spent.

"Many communities are plagued by drivers breaking speed limits and putting lives at risk. This investment would help to protect communities, particularly vulnerable road users such as pedestrians and cyclists."

News of more cameras comes as West Auckland residents were concerned that four fixed speed cameras decommissioned by police following faults with sensors wouldn't be operating in the area until next year.

"Police are working through a replacement process for the current fleet of static cameras and will be replacing them with a modern digital camera-based system, rather than the current wet film-based technology," Waitemata road policing manager superintendent John Kelly said.

"The replacement camera is radar-based, so does not require the placing of under road sensors, offering a more efficient and economic system.

"We are currently investigating where the need for speed cameras is and whether the ones we currently use are in the correct position."

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