Some Metro employees are receiving back pay after the transit agency banned them from driving buses until they could undergo a study for sleep apnea.

One worker received 176 hours -- more than four weeks -- of retroactive pay after waiting weeks for a diagnosis, according to an arbitration settlement between Metro and its largest union.

The arbitration panel ruled that Metro could continue to screen employees for sleep disorders but needed to provide temporary provisional cards so workers could work while waiting for a sleep study. It also said it would consider awarding more back pay in individual cases.

Obstructive sleep apnea is a concern because problems with breathing disrupt nighttime sleep, leading to fatigue during work hours. That could be deadly when someone is operating a bus or a train, as other transit agencies have found.

But Metro and its largest union have been battling since at least 2010 about the issue. Amalgamated Transit Union Local 689 was not arguing over whether employees should be able to drive if they have sleep apnea, or even if they can be tested, but whether they should be compensated while waiting to be tested.

Metro had been testing employees who had reported problems such as falling asleep on the job, but the transit agency started screening employees even if they had no known problems during a physical exam when their required commercial drivers' license recertification came due. Workers were ordered to undergo a sleep study to confirm a diagnosis.

If diagnosed with a sleep disorder, employees would have to demonstrate that they were following a treatment plan if they wanted to continue operating a bus.

But the union contested Metro's practice of putting workers on leave without pay, or using their sick and vacation time, while they waited for a diagnosis. The union argued that the sleep studies could take some three months to complete due to a backlog.

And the union argued that some employees were placed on leave when they merely had physical characteristics -- such as being overweight, having a thick neck, small jaw or "advancing age" -- rather than showing symptoms.

In one case, the union said, a woman had to wait about 14 weeks because her Metro-specific HMO and doctor did not agree with Metro that she needed a sleep study based on her body mass index and an apparently small airway.

But Metro said its screening method worked. That woman was ultimately diagnosed with a mild case. And 83 percent of the 137 employees pulled out for additional tests during the recertification process showing at least a mild form of obstructive sleep apnea. However, 17 percent did not have the condition. Metro also argued that giving workers unlimited paid administrative leave would give employees an incentive to delay diagnosis.