Cameras along a 160 metre length of bus lane in Auckland's Newmarket generated $4.3 million in fines during 2021.
Almost 29,000 fines of $150 were issued, due to people driving more than 50 metres in the Khyber Pass Road bus lane.
This worked out to almost $12,000 worth of fines per day.
AA's policy director Martin Glynn called the figure "huge".
"It seems massive for a short bus lane. Something's not right and it needs to be looked at."
The number of fines issued in 2021 was three times more than were reportedly issued in the same stretch for the 12 month period from November 2016 to 2017.
Driving in a bus lane is illegal, said Auckland Transport's group manager of parking services, John Strawbridge.
"Travelling by bus allows more people to move around the city," he said. "Faster public transport times will attract more patronage on public transport which will reduce congestion on our roads."
He said extending the bus lane operating hours, and the use of automated cameras had played a part in the increased number of fines generated.
Habits changing due to Covid-19, were also a reason.
"As a result, Aucklanders have spent the past couple of years taking an increased number of trips in their cars when they would have previously travelled on public transport, although this trend has started to reverse in recent weeks."
Motorists stung by fines have previously questioned the effectiveness of the signage on the bus lane.
In 2020, Damien Christie treated his children to a weekend morning show of the Sonic the Hedgehog movie. He said the streets were quiet, with no buses in sight. He shifted into the left-turning lane and thinks he travelled about 70 metres in the bus lane.
He didn't think anything of it at the time. Previously, the bus lane had only operated during weekdays. He was shocked when a fine arrived in the mail a few weeks later.
"The problem was the signage there. It's so hard to know where the bus lane starts and ends."
When he went back to look at the lane, he said he found signs twisted in the wrong direction and the green paint, often used to indicate a bus or cycle lane, worn and peeling in places.
"There was actually literally a chunk of the paint sitting in the gutter that had washed away."
Signs were now facing motorists and the surface of the road had been repainted green.
Christie said he was a cyclist and an occasional public transport user. He thought bus lanes were a good idea but on hearing almost 29,000 fines were issued in 2021, he thought signage on the lane still wasn't clear enough.
"Sometimes you get the sense that it is just absolute revenue gathering. I don't think there's any way they can justify that level of fines, that number of fines. They're obviously not clearly letting people know this is where the bus lane is."
Auckland Transport's Strawbridge said 6 million vehicles a year travelled along Khyber Pass Road "of which only 1.24 percent of road users on it are non-compliant".
He was confident Auckland Transport's signage complied with legal obligations, but said sometimes it took enforcement to drive the message home.
"Although signage plays a vital role in helping ensure drivers comply with measures like Special Vehicle Lanes, we do sometimes find that it takes a person receiving an infringement notice to drive real behaviour change and vigilance around Special Vehicle Lanes."
He rejected suggestions the lane was a revenue gatherer.
"In the case of Khyber Pass Road, the goal of our compliance activities is to help Aucklanders travel efficiently and effectively through Newmarket by bus. Our primary consideration is the effectiveness of our transport system - revenue is not our focus."
The Automobile Association's Martin Glynn said any bus lane generating large numbers of fines should raise a red flag to Auckland Transport.
"These figures are huge. The numbers you outlined are about 10 percent of all revenue across all the enforcement activities last year, that includes all parking fines."
He described it as a tricky intersection, with a very short bus lane.
"Drivers on Khyber Pass Road wanting to turn left have got very little space in the left lane to comply with the 50 metres rule before they reach the intersection."
While Glynn said Auckland Transport had been clear bus lanes weren't aimed at revenue gathering, the organisation needed to be aware of the public perception.
"Auckland Transport should be measuring success on how they can increase compliance, get the infringement rate down and bring the public with them. Otherwise, people will just see it as revenue gathering."
Strawbridge said Auckland Transport takes a "continuance improvement approach" to enforcement, and would carefully consider improvement requests it received from the community.
RNZ's The Streets Have Eyes project on CCTV cameras, revealed Auckland Transport was New Zealand's biggest spender on outdoor cameras among local and central government agencies. From 2017 to 2021 it spent more than $10m installing cameras.
It owns 3574 cameras.
In 2020, The New Zealand Herald reported between 2015 and 2019 the number of Auckland bus lane fines increased almost 1000 percent. About $2m worth of fines were issued in 2015, compared to $19.8m in 2019.
This increase was partly attributed to greater use of CCTV cameras.
Strawbridge said revenue from fines helped fund public transport, parking, road safety campaigns, walking and cycling initiatives and road maintenance.
"With Auckland Transport utilising the enforcement revenues collected in this way council is also able to allocate funding Auckland Transport would have otherwise needed, to other council services like libraries, parks, community centres, the Art Gallery, the Zoo, and other recreational facilities."
He said Auckland Transport had not pocketed the full $4.3m. As well as unpaid fines, each fine cost $30 to lodge with courts. The government also took 50 percent as a levy.
Damien Christie unsuccessfully challenged his fine, turning his trip to the movies into a pricey outing.
He said his children loved Sonic the Hedgehog but "I don't know if it was worth $150 on top of everything else, the popcorn is expensive enough."