A single queue is a principle that groups all customers or users into a single line before directing them to various checkouts, counters, or service points. When customers are at the front of the queue, near the checkouts, a digital display or an employee guides them to the available counter or service point. Initially used in public services and by the French National Railway Company (SNCF), this concept has spread to traditional retail and supermarkets. In supermarkets, it is often used for self-checkouts, although it is somewhat more complex for traditional checkouts.

This single queue system offers several advantages. It reduces overall waiting time by more efficiently directing customers to available cashiers or advisors. This improved productivity translates into potentially shorter waiting times for customers, as well as a possible reduction in checkout costs. Furthermore, the single queue helps to lessen the perceived wait time because it moves steadily. In terms of customer experience, it avoids the frustrations often associated with waiting. Furthermore, due to the large number of people in the queue, the displayed wait times become more reliable, as significant discrepancies related to certain customers are offset.

However, the single queue has a limitation: it can seem intimidating to unfamiliar customers because it may appear longer. Introducing this concept to customers requires clear and effective communication. For example, displaying wait times in FNAC stores can be a way to introduce the single queue. Service providers can also offer solutions for implementing this system, as illustrated in a case study from a large retail environment.