Nexar wants to create a database of driving behavior. (Keith Srakocic/AP)

The idea behind app Nexar is ambitious: create a type of air-traffic control system for the road. Catalogue the cars in a given location, track dicey behavior and help drivers avoid dangerous intersections and even bad drivers.

Nexar is a free dashcam app that, using artificial intelligence, creates a database of an area’s roads and drivers. If car stops short in front of you, even a few cars in front of you, Nexar’s database can send you a notification so you’ll have more time to brake. If an accident happens around the corner and cars are getting detoured onto your route, the app will tell you.

And soon, if the app detects a bad driver on the road near you, it will also tell you where they are.

“My oldest daughter will be driving in four years or so, and we thought there’s no reason why today we still have car accidents,” said co-founder and chief executive Eran Shir. “We have all the of the technology right now to get rid of more car accidents. It’s really a matter of putting things together and bringing it to market.”

All that sounds great -- who doesn’t want safer roads? -- until you factor in the somewhat outsized privacy implications of the app.

[The big data of bad driving, and how insurers plan to track your every turn]

What if the “bad driver,” according to Nexar’s algorithm, isn’t a bad driver at all? What if it’s a teen who borrows his mom’s car? Would every minivan soon be labeled reckless?

Perhaps.

“We’re losing some of the granularity between car and driver that we’ve had in other contexts,” said Andrea Matwyshyn, a professor of law and computer science at Northeastern University.

What if “bad drivers” get tracked using the app’s notifications? Do you have the right to know where any given driver might be at any time, even if he or she is on the other side of town?

In a word, yes.

“Imagine if this was 50 years ago,” Matwyshyn said. “Nothing would stop a driver from keeping a little black book of all the cars they come across. We might have thought that person be a little overzealous, but today, this app is that version of the little black book.”

And what if insurance companies get ahold of information from Nexar’s database?

They will.

According to Nexar’s privacy policy, “We also may share driver ratings with, or use Personal Information we collect regarding drivers (whether users or not) to advise, insurers for purposes their underwriting or other evaluation, but always in compliance with all applicable laws.”

In other words, an app is going to collect your license plate information, tie it to your known locations and whereabouts and make judgments as to whether or not you’re a good driver, and that information will be shared with insurance companies.

[Honk if you think drivers should be more courteous]

Is that a worthy price to pay for safer roads?

Shir says it is. Already in San Francisco, New York and Tel Aviv, Nexar has catalogued 7 million cars and adds 100,000 more to its roster each day. It’s moved on to keeping track of potholes.

“Anything that we can get our hands that is meaningful from a safety perspective we want,” he said.

That kind of capability could be useful, Matwyshyn said, but it’s up to individuals to decide whether they’re willing to surrender that kind of personal information.

Increasingly, our everyday transactions have less to do with goods or services and more to do with personal data, which enables the future sale of goods or services. Think about when you pay cash for a Father’s Day card at the drugstore. A clerk might ask you for your email address or phone number.

The actual transaction doesn’t matter as much anymore, Matwyshyn said. The data matters.

“This is an area of information access that we’re still working out as a society,” she said. “I think our baseline is shifting.”