What might seem like an obscure topic is actually one in which we are all affected: The Science of Lines. You can also view all 40+ articles on Queueing Theory.
Reflect for a minute: We wait at the retail checkout line – in all stores in which we buy stuff. In retail, the congestion is worse at the end of year holidays. A line at an amusement park is likely busy during the Summer months. So on and so forth.
So, how does a customer experience waiting and what is the effect of waiting on commerce and buying?
In general, once a wait last longer than 3 minutes, the perceived wait time multiplies with each passing minute. Shoppers who actually waited five minutes reported having waited twice as long. This is the Psychology of Queueing.
If customers have to wait, why not make it a revenue opportunity. That’s exactly what most of us experience at the retail checkout line. Need a chap stick? What about that stuffed animal you never would have thought of buying, but are now thinking about it while you have to wait in line. Oh, wait, what about those batteries you don’t need for anything – yeah, just buy some just in case.
That’s what retailers are capitalizing on: if you have to wait, then make the wait feel less so and make it a revenue opportunity.
If a line is short, it’s probably because of a customer or other circumstances that is making the ability to serve take longer. For example, today I was at Sam’s Club where I was in position #4 from the checkout. The customer at the checkout counter was arguing about something, making the line longer. So what happened? Customers on my line left to other lines that were perceived to move faster – not necessarily shorter lines, but lines that were perceived to have higher velocity.
Balking is technically the state wherin a person who would otherwise have entered a line, decides not to enter it. This is typically a customer who is about to enter a line and surveys the available lines. They consider the wait time, look down at what they’re buying, does a cost or benefit analysis on waiting versus the benefit of buying your items. Sometimes, the customer will put down their items and just leave the store, concluding that waiting isn’t worth it.
The technical definition of Reneging in the context of Waiting Lines is when a person enters a line, then leaves it before being served. This is similar to Balking, but where the customer has chosen a line, but then leaves it after they do the cost and benefit analysis in their mind on whether the wait is worth it.
Below is a nice infographic on the Science of Waiting Lines 1
- http://online.wsj.com/article_email/SB10001424052970204770404577082933921432686-lMyQjAxMTAxMDAwODEwNDgyWj.html?mod=wsj_share_email ↩
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Michael Sherwood says
I was actually going to a store this weekend and saw a full parking lot. At that point I chose to go to another store because I imagined the lines that the store would have. The other store I went to had an emptier parking lot and I didn’t wait in a line at all. Even though I have to drive another 2 miles to get to the store I am planning on going there for my next grocery trip.
Brian Beebe says
I don’t know if I’m buying the one line vs. multiple lines comparison. The image is not an apples to apples comparison.
1) Different amounts of customers
2) Different amounts of cashiers
Try this image – which line would you rather be standing in?
* 5 Cashiers
* 30 Customers
* 23 regular customers
* 7 Stoppers
* 4 Customers and 1 Stopper SWIP for both
* 15 Customers served before all aisles stopped (Parrallel/Multiple Lines)
* 13 Customers served before all aisles stopped (Serial/Single Line Flow)
* Customer Perception – Single Line is 5 times as long (but moving)
* If customers are viewed as WIP, there is more transportation/travel from a one piece flow perspective… (Parrallel/Multiple Lines) 6 Body Positions to completion (Serial/Single Line Flow) 26 Body Positions to completion
Please notify me if the photo link does not work.
James Lawther says
Pete, I read once that the best way to keep customers happy in a queue is to put up a mirror, then they become too busy looking at themselves to notice the passing of time.
I work in a call centre, we obsess about queues, unfortunately mirrors won’t work for us.
What is there are 3 back to back line stopper customers. In that case you would have 3 stations blocked. One Line vs Multi-line logic doesn’t seem to work for me.
Greg Watts says
The maths of single vs multi line have been proven many times. I believe (and am happy to be proven wrong) that the original work was done in banks. The key figure is the Average wait time per customer. With a single line the distribution of wait times is much narrower and is only affected by the number of people within the line, leaving it and joining it. With multiple lines you have to add in the’tolerance’ wait time before swapping and the fact that in a line with a blocker, everyone in that line suffers the additional time, not so with a single line as unless you get a blocker at each till/service point, the line will continue to move (statistically unlikely). With multi lines the issue is that people tend to wait too long before swapping lines because they have invested time and there is the ‘fear’ that if I swap, the line will start to move quicker because the blocker finishes. The same has been shown on motorway queue’s occupying all lanes. It is better to stay in one lane because the very act of swapping speeds up the line you leave and slows the line you join (average times). It is all very counter-intuitive.
Lecture over! : ) Reading it back it I really do think I need to get out more.
Israel Robert A. says
“…..Pete, I read once that the best way to keep customers happy in a queue is to put up a mirror, then they become too busy looking at themselves to notice the passing of time. I work in a call centre, we obsess about queues, unfortunately mirrors won’t work for us”……..
sorry! this may not work. Anytime i go to the bank hall and meets a long line, i noticed customers rather sit comfortably watching television than time.