State-of-the-art cameras popping up on billboards around the country are tracking the number of times and types of vehicles that pass them in what is believed to be a world first.
The company behind the billboards is adamant the technology complies with privacy rules.
However, civil liberties experts say cameras using automatic number plate recognition (ANPR) to collect data on motorists' vehicles raise privacy issues and may be a step too far.
It comes amid growing concerns about how much private information people are giving away digitally and how it is being used.
This includes what is happening with the vast amount of information being collected by the Government's NZ Covid Tracer app and social media platforms such as Facebook and Twitter.
The new LENS cameras launched in September last year, and used on all 25 LUMO billboards around New Zealand to provide marketing insight to media companies and companies using them to flaunt their goods or services.
Most of the sites are in Auckland but there are also two sites in Christchurch and one each in Hamilton, Tauranga and Wellington.
LUMO co-founder and chief executive Phil Clemas said the main reason they started rolling out the LENS technology in September was to measure audience. Like with all media platforms, advertisers wanted to know how many people would see their ads and how often.
Since the company's inception, it had been monitoring real-time traffic volumes but the new technology gave insight into the frequency of the vehicles going past and - paired with data purchased from NZTA - also the model, make and year of manufacture of each vehicle.
"We don't know demographics. We don't capture any private information - we don't go deeper than that."
While advertisers could make general assumptions that a person who drives a certain car might like a certain product - the main interest in the new data came from the automotive industry.
For example if Mazda wanted to advertise a new car it could work out how many Mazdas drove past each billboard site to better target marketing, he said.
He said LUMO strongly abided by privacy laws and made it clear to clients that it didn't track any individual number plates or collect any private information.
However, NZ Council for Civil Liberties chairman Thomas Beagle had concerns about privacy.
"We think there are some real privacy issues around capturing and storing this information especially where people are just driving into a street."
While the technology could be valid in a private carpark or building to check vehicles were parked in the right place and for the right time, he felt tracking people's movements on public roads was a step too far.
"You can tell where people were at that point at that time. If you've got multiple billboards or cameras around they can start tracking their movements through the city and personally I think that goes a bit too far.
"The ultimate end game of this is someone setting up a system where if they put up enough cameras they can tell where everyone is going at any point and I don't think we want that."
He argued that a number plate could in many cases be private information because it usually linked back to a person.
Buddle Findlay partner Tony Dellow, who specialises in privacy law, said collecting number plate information would comply with the law unless it linked to identifiable information about an individual - which the company says is not happening.
The grey area was whether there were sufficient safeguards to ensure the collection of information did not identify individuals, or where they had travelled at a particular time.
AA principal adviser Mark Stockdale agreed there wasn't a privacy issue if the company was only collecting vehicle data, but questioned what value there was in having details about which types of cars were going past billboards.
"We would certainly be concerned if they were getting access to owners' details so they could contact them. That would be wrong and providing that it isn't happening then there is no great harm."
Auckland University associate professor in marketing Mike Lee said the main benefit in the technology was providing a solid number of how many cars had passed a billboard in a certain time period.
He said the company didn't necessarily need to know who the person was. It just needed to approximate what income bracket they were in and what demographic drives what kind of vehicle to help target marketing campaigns.
Lee felt there was a limited use for that type of information. But it could assist those selling advertising on the digital billboards, for instance to companies targeting soccer mums if an area had many SUVs.
But if advertisers really wanted to target ads to a specific demographic there might be better tools available such as social media, Lee said.
The Office of the Privacy Commissioner said it was unable to comment without more information about the new technology.