The pilot program, which launches in Los Angeles and eight other cities Friday, uses a smartphone's motion sensors and gyroscope to track drivers who speed, slam on the brakes, cut corners or text while behind the wheel.
Drivers will receive a daily report summarizing how often they brake harshly or exceed the speed limit. The software also works in real time, notifying drivers immediately if they are 15 mph over the limit.
Uber says the information isn't being used to penalize drivers, but rather to help boost the ratings they receive from passengers. The San Francisco company can bar drivers whose ratings fall too low from using the app.
Uber tested the program last year in Houston by looking specifically at braking behavior and emailing feedback to drivers.
Similar programs, known as telematics, are used in the trucking industry to monitor drivers.
Uber already retained the smartphone data before launching the program, and drivers were informed during the outfitting process that Uber "may monitor, track or share their data." Drivers can't opt out of the program.
Though Uber is framing the policy as the latest in a series of tweaks to its app intended to improve the experience for drivers, some are concerned it represents a violation of their privacy.
"When I first heard of the program, it seemed a little bit invasive," said Harry Campbell, a part-time Uber driver and a blogger at the Rideshare Guy. "I think you sort of have to agree to some of that to work with them in the beginning, but it starts to feel that Uber has a lot of control over you."
Control is a big question for Uber, which has grown into a company valued at $62.5 billion thanks to a business model that classifies drivers as independent contractors rather than employees eligible for benefits. A key difference between employees and independent contractors is the level of control a company exerts on the way they do their jobs.
Uber is seeking a settlement of as much as $100 million in a class-action case filed by drivers who want to be considered employees.
Campbell said although the program could help improve driver safety, the company has a rating system in place that could do the same if it were altered to provide drivers with more feedback from passengers.
"Drivers aren't going to be super happy about it, but there's not a whole lot they can do," he said. "It's more of a nuisance than anything."
2:58 p.m.: This article was updated with staff reporting.