For 24/7 operations, the easiest way to create a high-overtime schedule is to reduce the number of crews. That's because there is an inverse relationship between the number of crews and the average weekly hours the employees have to work as shown below: 

Crews        Hours

   3                56

   3.5             48

   4                42

   5                33.6

I don't recommend using schedules with that much overtime. People that do this claim it's temporary or it's a common practice in their industry. I explain that high overtime schedules cause problems in the following areas: safety, quality, and employee health. There is also the risk of liability for an employee who crashed his or her car on the commute home after five or six consecutive night shifts.

Every month or so I get a call from someone who wants to run a schedule that would normally take 16 people, but they only want to use 12 or 14 employees. They ask me to give them a pattern (like 4-on-2-off) that would work. Instead of focusing on the pattern, they should start by deciding the number crews – either 3 or 3.5 crews.

I see this a lot with fire departments and paramedics. They work 24-hour shifts, and want to know if a 2-on-4-off pattern or a combination of 10 and 14-hour shifts would reduce the overtime. I explain that they need to start with the desired weekly hours of work and select the number of crews that comes closest to that target. Then and only then can they start searching for a work pattern (or different shift lengths) that provides the desired coverage.

I ran into the opposite situation recently with a major airport. Their screening officers were assigned to 5 crews on an 8-hour rotating shift schedule with a 3-on-2-off pattern. Management wanted to get more coverage without hiring more employees. I suggested 4 crew patterns that averaged 42 hours a week. By increasing the average weekly hours from 33.6 to 42, they were able to increase the coverage from 56 to 70.