If single lines reduce wait times by so much, why do stores queue us in separate lines for each cashier? One reason is that models overestimate the difference between single and multiple lines because they don’t take into account some human behaviors. Maybe you know who the fastest cashier is. Maybe you switch lanes (“jockeying”) or simply ditch your items and leave (“reneging”). Those behaviors reduce the average wait time in a multiple-line queueing system and bring it a little closer to a single-line system.
In addition, perceptions don’t always match up with reality. The longer we stand in line, the more the gap between perceived and actual wait time grows. By the time we’ve been in line for 5 minutes, we think we’ve been waiting for 10. (See “Why We Buy,” by P. Underhill). So rather than simply shoving us all into one line, supermarkets are exploring three alternatives to reduce both our actual and perceived wait times. First, customers waiting in line can have their items scanned by roaming tellers with hand-held machines, to reduce their service time once they finally reach the cashier. Second, customers can register their place in line, go away, and come back once it’s their turn (like grabbing a ticket from the deli counter). The 3rd strategy: distraction. You can try to entertain customers with videos and in-line merchandising.
Classroom discussion questions:
1. What is the main reason supermarkets do not use a single checkout line?
2. What other alternatives can stores use to speed up the lines?