Police in Essex County have started using licence plate scanners. Here's how they work

As senior constable Justin Pare drives around in his LaSalle police cruiser, a sudden sound of a siren pings on his laptop. That happened 48 times in just 30 minutes using licence plate scanning cameras, signalling dozens of violations from passing vehicles.

Automated licence plate reader (ALPR) technology is now much more widely used since the OPP in southwestern Ontario installed it last month.

In Essex County, approximately 50 front-line police vehicles are now equipped with the cameras mounted to the top of the cruiser.

A single cruiser in LaSalle has been using the infrared cameras since 2018 after applying for and receiving a provincial grant. 

Past due plates and expired drivers' licenses are the most common infractions they discover.

However, it helps police with more serious issues such as finding stolen vehicles, wanted suspects and missing children when an Amber Alert is issued.

"All it is, is another set of eyes for us so that we can keep our eyes on the road," said Pare.

WATCH: CBC News went on a police ride along with Pare to see first-hand how the technology is used.

During the ride, CBC News saw dozens of violations, also known as hits. Those all consisted of expired plates, which would be a $110 fine in Ontario, or expired licences, a $325 cost for motorists.

"It shows me the picture of the front end of a license plate and a brief description of the car, which I can see it matches and I can be satisfied that's one in the same, and I can move forward with a traffic stop," said Pare.

An alarm sound comes from the officer's laptop when a vehicle passes that may be connected to a traffic or criminal violation.

He said while the cameras do capture the vehicle and the licence plate, it does not take a picture of the driver for privacy reasons.

The province stopped mailing out renewal reminders as of March 1, 2022.

Also last year, Ontario scrapped the need to pay to renew license plates or put a dated sticker on them — although they still need to be renewed.

"We hear feedback from the motorists on the roadway that 'I didn't get the letter in the mail no more. They don't tell me no more,'" said Pare. These traffic stops, he said, are sometimes educational ones.

With these cameras, it now makes it easier for police to spot expired ones.

But it also raises privacy concerns.

License plate readers raise privacy concerns

The Information and Privacy Commissioner of Ontario released a report in 2017 outlining how police should and shouldn't use this technology.

It says officers should not use the data to track the location and movements of law-abiding citizens.

Gautam Kamath is an assistant professor at the University of Waterloo. He researches data privacy and has similar concerns.

"The main issue it brings up is the feeling of constant surveillance and the associated privacy risks. I think in general people should have the ability to move around freely without the feeling of being constantly surveilled automatically," said Kamath. 

"Many people might say that the police already had similar power, they could look up any individual license plate, but I think the ability to do this en masse is a bit troubling and worrying in terms of individual freedoms."

LaSalle police says any licence plate capture with its camera that doesn't trigger a violation is purged from the system within 24 hours. If it does, that's kept for five years for court and evidence purposes.

The Ontario government says it's spending $40 million to provide 40 municipal police forces with ALPR technology, which can read thousands of license plates per minute.

The Windsor Police Service equipped one of its vehicles with licence plate reading technology in October of 2020.