I am asked all the time, “Are longer shifts better?” More commonly, the question is, “Isn’t it true that 12-hour shifts are more dangerous (or less productive) than 8-Hour shifts?” It depends.
Given a choice, most employees I encounter – and it doesn’t matter what their job is – would like a schedule that gives them more days off. The only way to get more days off with the same paycheck is to work more hours in fewer days. For example, if you work four 10-hour shifts, you work two hours more on than an 8-hour shift for four days and reach 40 hours of work for the week one day sooner. That’s 156 days off per year on a 10-hour shift compared to 104 days off per year on an 8-hour shift for the same 40 hours of pay per week. For those that want a lot of days off, the logical extreme is to work 12-hour shifts which result in 191 days off per year for the same 40-hour paycheck. More commonly, however, 12-hour shifts are designed to give employees an average of 42 hours of work per week. That means that there is 5 percent built-in overtime and the number of days off is 182 per year. An 8-hour schedule with 5 percent built-in overtime results in only 91 days off per year.
So is a longer shift more dangerous? This idea is a typical misconception. Safety data shows that periods around shift change experience the highest accident rates. People know this intuitively because of the experience it. They see the slow down of production and the accidents that happen – mostly near the end of their shift. So people on 8-hour hour shifts observe accidents occurring near the end of their shift and conclude that longer shifts must be more dangerous. In reality, when people start working longer shifts the most hazardous hour just moves to the end of their new shift. On a 10-hour shift, the tenth hour is the worst hour. But on 10-hour shifts the eighth and ninth hours are not any riskier than the second through the seventh. And they are better than the first hour of the shift which is almost always the second worst hour in terms of accident risk and decreased productivity. It turns out that independent of the shift length, the last hour is the worst for accidents, followed by the first hour as the second worst. I believe it has more to do with being disconnected with work on those hours. In the first hour, a workers mind may be on what happened before work, at the end of the shift the same worker may have already mentally left his job.
What about the business drivers? Are longer shifts better or worse for business? Once again, it depends. In companies where there are costs associated with the start and end of a shift, there are significant benefits for longer shifts. For example, in many mining operations, miners are paid to travel from the entrance to the place of work where they are actually mining. Since travel time is not productive, longer shifts mean less travel time and higher productivity. For example, if there are 30 minutes of unproductive time at the beginning of every shift and an operation goes from 8-hour to 12-hour shifts, they will automatically reduce the number of shift changes from 3 to 2, or an over 2% reduction in the per unit cost of labor. Shorter travel times (or less unproductive time) could result in negligible savings. Communication is often better on longer shifts as you only have to communicate to two shifts as opposed to three. Again, depending on the organization and communication processes it may be negligible.
Perception is actually the biggest hurdle for people to overcome when deciding to work longer shifts. Eight-hour shifts are still the most common shift length in the world. Most people first work a twelve-hour shift when they are asked to stay over for four hours of overtime on an 8-hour shift. If that happens one day, it may happen the next and the next. Working five 8-hour days with half of them being extended to twelves is not an excellent example of a 12-hour schedule. To make the right comparison, one must be exposed to a longer shift with the same weekly average; four tens, or three and a half twelves. It turns out that productivity is not linked to shift length at all. It is linked to average hours worked per week. Empirically, the highest correlation is with what people have done during the past five weeks. A few decades ago the US Nuclear Regulatory Commission did a study comparing different shift lengths working on the night shift. The study focused on the difference between 8-hour and 12-hour shifts. In the end, they found no statistical difference between shift lengths. Imagine that.
So, what is the better shift length? Let’s say it all together…”It depends. “ The bigger question is, “What do employees want?” Do they want to work fewer hours per day but more days, or do they want to work few days but longer hours on the days they work? Over the last few decades, people have continued show interest in moving to longer shifts. Very few go the other way. Just because most people want to do something, however, does not mean it is for everyone. I have surveyed thousands of employees working 8-hour shifts who have considered 12-hour shifts but continue using 8-hour shifts. The right answer is the right answer for a specific group of people. And to find that out you need to ask them. So, what’s stopping you from asking?