Drowsy drivers to be keep off the road says Uber.

Uber is ready for a less laissez-faire approach to drowsy driving.

The ride-hailing company is rolling out a new policy that requires US drivers to take a six-hour break after 12 consecutive hours of driving. Uber plans to enforce this policy with an app feature that counts down available driving hours, warning drivers when they have two hours, one hour, and 30 minutes of driving time remaining.

Uber told the Washington Post that hours spent online and driving will count toward the 12-hour limit. Time spent online but stopped, such as waiting for a ride at the airport, will not be counted. Uber also will not track time drivers might spend offline on its app but driving for a competing service, such as Lyft.

The company said in a blog post it's introducing the time limit to "do our part to help prevent drowsy driving." Uber has historically taken a more hands-off approach with its independent-contractor drivers, telling them they can "be their own boss" and "set their own schedule."

The US policy change comes a month after Uber introduced a similar policy in the UK, which logs drivers out for six hours after they work 10 in a row. Uber had previously pushed back against the idea of capping driver hours, saying, "Uber does not set hours or shifts and drivers who partner with us can choose the hours they work." The change was likely motivated by a string of recent setbacks for Uber in the UK and Europe, including London's transport authority declining to renew its license to operate in September 2017, citing consumer safety concerns.

In the US, Uber had capped driver hours in just a small handful of cities, including New York and Chicago.

Uber imposed a 12-hour limit on its New York drivers in February 2016, after the New York Post reported that some drivers were pulling 19-hour shifts. While adopting new rules to restrict fatigued driving that year, the New York City taxi regulator reported that the crash rate for taxi drivers working more than 12 hours a day was 24% higher than the crash rate for drivers working 12 or fewer hours.

In April 2016, Uber partnered with media mogul and soon-to-be Uber board member Arianna Huffington on a campaign "to end drowsy driving." The campaign was aimed at sleep-deprived office workers, rather than Uber drivers, who Uber encouraged to call a ride through its app instead of getting behind the wheel.

Huffington, who has made sleep a pillar of her personal brand, visited college campuses around the country for the campaign to offer "sleep tutorials."

In 2017, Uber fought a proposal in Massachusetts to limit drivers to 16 hours a day, or 70 hours a week, calling it (pdf, p. 10) "unworkable" and "overly burdensome." The company, which filed the comment under a subsidiary name, argued that ride-hailing was "inherently flexible" and that "rigid hour limits without an underlying safety rationale are antithetical to that flexible model."

In an October 2017 report, the US National Highway Traffic Safety Administration (NHTSA) said drowsy driving accounted for 2.3% to 2.5% of all fatal crashes from 2011 to 2015. NHTSA describes drowsy driving as "a profound impairment that mimics alcohol-impaired driving in many ways."

Lyft has required drivers to take a six-hour break for every 14 hours spent in driver mode since January 2014. Many US cities also regulate the number of hours taxi drivers can work, though those restrictions typically haven't applied to app-based ride services.