OM in the News and Video Tip: The Psychology and Math of Queuing in Supermarkets
You dash into the supermarket for a few quick items. But when you get to the checkout lanes, they are full. Your plan for a quick exit evaporates. For anyone who has ever had to stand in line at a supermarket, here are some tips from The New York Times (Sept.8, 2016) for picking the line that will move the fastest.
- Get behind a shopper that has a full cart. That may seem counterintuitive, but every person requires a fixed amount of time to say hello, pay, say goodbye and clear out. That takes an average of 41 seconds per person and items to be rung up take about 3 seconds each. So getting in line with many people who have fewer things can be a poor choice. (One person with 100 items will take an average of 6 minutes to process. A line with 4 people who each have 20 items will take an average of 7 minutes).
Study the customers ahead of you. It is not just the number, but their age and what they are buying. Older people will take a bit longer because they can have technical difficulties that delay the process. Also consider the number of different items they are buying. Six bottles of the same soda will go faster than 6 totally different items, some of which cannot be scanned, such as vegetables.
Choose a line that leads to several cashiers. In Module D of the text, we show that this approach, known as a serpentine line, is the fastest. The person at the head of the line goes to the first available server in a system often seen at airports or banks. Getting into a single line also provides psychological relief because it eliminates the choice of where to go and second-guessing about the best line to choose. Your students will love this 90 second queuing video.
- The psychology of queuing has also found that waits seem shorter when you are distracted. Try talking to the person next to you or reading the magazines in the store’s racks.
Classroom discussion questions:
- Why is the “serpentine” line faster on average?
- What does Disney do to keep visitors happy during 45-minute lines?