When we are approaching the checkout in the supermarket how do we decide which queue to join? Is it the shortest? Is it the one with the fewest number of full trollies? Is it the one that is staffed by the most competent looking operative? Or is it the new-fangled computerised one that technophobes like me avoid like the plague? If our goal is to get out of the shop as quickly as possible then this is an important yet tricky decision. Once we have committed to a specific queue then we are bound by the social norms to stick it out.
Technically speaking the queue to join is not the shortest one, or the one with the where there are the smallest number of individual items that need to be scanned, or the one with the fastest operative – it is the queue with the smallest load – the cumulative product of the number of items and cycle time of the operative. Hence our quick mental calculation of length of queue * average size of trollies * speed of operative. Even then it can go wrong if someone throws a spanner in – such as picking up the only item on the shelf with a missing barcode – triggering the need to call a “supervisor”!
Are we completely powerless in this process? Not at all – we each can ensure all our purchases have barcodes and we can also influence the cycle time of the operative. Observe what they are doing – picking up each item in turn, finding the bar code, and turning the item so that the bar code can be easily scanned by the computer. To shorten the cycle time all we have to do is make the work for the operative as easy as possible by placing each item on the moving belt in the correct orientation and spaced so that the speed of the belt delivers the items at the same rate that the operative can scan. This sounds counter-intuitive but it works! It is just like the variable speed limits on some motorways – by slowing down you get there faster because the flow is smoother – there is less “turbulence” created.
There are two potential flaws in this counter-intuitive strategy though – the people in the queue behind you may start “tutting” because they believe you are playing childish games and slowing the process down (which is incorrect but we are social animals and we copy other people’s behaviour and react to “social deviants”). The other flaw is that, if I am shopping alone I cannot both stream my purchases for optimal scanning and also pack my scanned purchases into my reusable shopping bag! So, I may only be able to use this strategy when accompanied by a trained assistant and have access to my fast getaway car! Of course I might get even more radical – and offer to stream the shopping for the person in front of me while they pack their scanned items. But that would mean that we work together to achieve a common goal – to reduce the (life)time we all spend waiting in the shopping queue. This way we do not need an assistant or a getaway car and shopping might even become more sociable. Everyone wins. What everyone? How is that possible?