The mayor says he is looking for answers on how overtime is handled at Calgary Transit.

recent City of Calgary auditor's report suggests that worker shortages, in part because employees called in sick, caused Calgary Transit to add nearly 150,000 hours of work in 2011.

Mayor Naheed Nenshi said the union makes a fair point that transit drivers face greater exposure to illnesses, but he still wants more information.

"I really want to look at our absenteeism, not necessarily versus other departments, but much more versus other transit organizations across the country and around the world and see how our numbers stack up," he said.

Calgary Transit employs roughly 3,000 employees and about 2,000 of those volunteered for overtime in 2011. In the report, auditors say the authority exceeded its overtime budget by 71 per cent in 2011 and 29 per cent in 2010.

The report found that the average overtime paid in 2011 to operators was $3,596.

Three operators earned more than $30,000 in overtime pay and another 21 operators earned more than $20,000.

Council's audit committee will discuss the report Thursday.