The 50kmh speed limit on Port Hills Rd was changed to 60kmh in 2011, but the signs were never changed.

Seven years worth of speeding fines issued on a Christchurch road could be deemed invalid after police ticketed drivers based on the wrong speed limit.

The 50kmh speed limit on Port Hills Rd, from Garlands Rd to the Tunnel Rd intersection, was legally changed to 60kmh by the NZ Transport Agency (NZTA) in March 2011, but the signs were never changed so police have been ticketing people based on a 50kmh limit.

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GEORGE HEARD/STUFF The NZ Transport Agency has changed the speed limit signs on a 2.8km section of Port Hills Rd from 50kmh to 60kmh after it was discovered the signs were incorrect for seven years.

The error was discovered when police were preparing for a court hearing for a speed offence on the road.

NZTA system manager Pete Connors said the 60kmh speed limit was published in the New Zealand Gazette three weeks after the February 2011 earthquake. The new limit took effect one month after publication and new signs should have been installed at that point.

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However, due to the focus on earthquake recovery and competing priorities, the new signs were not installed, he said.

NZTA installed new 60kmh signs on Thursday last week.

"The new signs rectify an historic error in the speed limit signage."

Police were now trawling through seven years of infringement notices issued on the 2.8-kilometre stretch of road to identify any that were invalid as a result of the incorrect signage.

Police road policing operations manager Inspector Peter McKennie​ said the process would take time.

"It is important that police is thorough with this process to ensure we don't miss any notices that need to be rectified."

McKennie said any infringement notices found to be invalid would be cancelled and any fees that had been paid would be refunded.

He would not say how many people were likely to have received incorrect fines.

"Police will make contact with affected drivers by mail in due course."

McKennie said people would be refunded into the account they were paid from and if police did not have the account details they would contact the recipient to obtain them.

Demerit points issued would be removed from the driver licence record by NZTA.

A Christchurch woman, who did not want to be named, said she had received two fines for travelling at 61kmh and 64kmh on that stretch of road during the past seven years.

She said police targeted people for speeding for a good reason, so she was not too upset at the mistake, but would accept any refund she received by police.

Changing the speed limit signs on Port Hills Rd has added to concerns about safety for cyclists using the road.

Heathcote residents have called on the Christchurch City Council not to delay construction of the Heathcote Expressway cycleway because it would provide a safe route for cyclists away from the busy road.

During a long term plan (LTP) submission hearing last week, Heathcote resident Chris Ansley said the only way in and out of Heathcote was a "gauntlet of expressways", which were not child-friendly and frequently used by heavy trucks.

He was disappointed the council was proposing to delay construction of the cycleway until 2026-27.

Myles Mackintosh echoed Ansley's concerns at an LTP hearing on Saturday.

His family had one car and his wife cycled to Opawa School most days carrying their children on a cargo bike, because it was "too dangerous" for the kids to ride their own bikes.

"It's a nerve-racking journey. Trucks and cars pass extremely close."