For some Uber drivers, long shifts have become the norm. Dropping fares and profitable incentives lure them to keep driving past safe limits. Because the ride-hailing service doesn’t set a cap on how many hours its drivers can work at a time, there are few legal ways to stop them. Rival Lyft shuts off its app, which drivers need to find customers, after 14 hours at a time and doesn't let drivers back on for six hours to let them rest.