Types of Human Queues
Talking about types of queues in general (human or non human) would require extensive research and a more elaborate write up. However, in this blog, I would like to mention about the various types of human queues which are being formed currently the world over, and also see some examples in each of the types.
Elements of a queueing system
If we deconstruct a human queueing environment, it consists primarily of 2 things.
1) The service provider (in classical academic language, its also called the server)
2) The humans who queue up for the service provider.
The types that we would talk about here arise due to variations in the following aspects:
a) Number of service providers
b) Number of queues
c) Having multiple types of services
d) Similarity or exclusivity of services provided by different service providers
e) Sensitivity to the differences in the types of humans queueing up
f) Simultaneous queueing up for multiple services
g) Allowing for preferences
h) An ordering or sequence amongst the service providers
i) Service times
j) Batching people
For simplicity, when I say type of queue here in this write-up, it would mean type of “human queue”.
Types of Queues
Single Counter Queue
The simplest type of queue gets formed when there is 1 service provider, and the visitors in the queue are queueing up to receive services from one service provider. We call this single-counter queue. For the purpose of this discussion, a counter simply refers to the service provider.
Symmetric Queue Counters
When we have multiple service providers, all of them offering same services, and the people seeking services queue up in a single queue, we call it a symmetric-counters-single-queue system. When people form separate queues for each of the counters, we call it symmetric-counters-multiple-queues system. In a symmetric counter system, all the service providers are capable of all the services that the business offers. A typical example of symmetric-counters queueing environment is found in service centres of mobile network operator companies, or at movie counters or at railway ticket counters.
When the counters or service providers in the queue offer entirely different types of services, then it forms an exclusive counters queueing system. A typical example would be a hospital's out patient department where patients line up for different doctors providing entirely different types of consultation. Even if the type of consultation for two doctors is same, the fact that the patient will generally not switch from the doctor whom he originally intended to see makes the service provider (doctor) exlusive. Typically, each doctor would have a separate queue. The hospital’s example above is actually that of an exclusive-counters queues system. Another example is that of a food court where the different restaurants at the food court offers different products.
A group of counters which provide similar services would be referred to as grouped counters. In the same premises, there could be other groups of counters offering somewhat different type of services, or services to different types of humans queueing up at the premises.
At a bank for example, it is usual to see a grouped-counter queueing system where a group counters would be capable of providing similar set of services. Of-course maintaining a separate queue for a different “group of counters" or "types of service providers” would be apt. However, for different counters within the same group or which provide the same kind of services, the usual practice is to maintaince a single queue. This practice is also supported by research.
One constraint of having a single queue would be that if people stood physically to maintain queue position, it might get too long, and the premise’s length (or breadth) would constrict the queue to fold, which is why physical queue managers become an integral part of the waiting area. However, a better way would be to manage this kind of crowding using a queue management software and installing a TV number display system integrated with it, which would allow people to sit on chairs mobilize a bit, being less bothered about maintaining the queue position physically by standing in line.
Human-types sensitive Queues
It is quite obvious that many businesses or organisations would want to maintain separate queue for different types humans queueing up for the services.
An example could be a bank queue being exclusively maintained for senior citizens, differently abled people and pregnant women. An extreme example is that of hospitals, where queues are skipped entirely for patients under emergency. And then there are other examples where VIP queueing is allowed, where people would pay a premium for a VIP queue. Some businesses may want to reward loyal and regular customers by allowing them VIP experience. A restaurant may keep some percentage of tables as reserved for VIP or regular guests, and try to allow them in earlier than other customers.
It is very essential for any organization to allow for enough room in the waiting area as well in thier queueing systems, to allow for exceptional scenarios.
The best example of group queues is that of a restaurant or a pub during peak hours, where a group of people would queue up together for a table. Here the queue positions are alloted by matching the table size to the group size.
A typical example of this is seen in a diagnostic centre. In a diagnostic centre’s flow, I could be queueing up for multiple tests, and these tests need not have any particular order, and all these tests are done in different counters. A person would obviously not feel comfortable to queue up separately for every test.
A typical example is that of a Salon’s queue, where the customer might be interested in a few services, and the customer would typically have a preference amongst the stylists. An important aspect here is that the person may not be too rigid on the preference, specially if the selected stylist has lot of customers waiting.
Another example of preferential queueing is found in restaurants, where there may be certain preferences of the customers on the seating area, like smoking or no-smoking zones, etc.
When there is an ordering between various counters or service providers, then each counter can referred to as a stage. Even though, counter has a physical presence, stage refers to “the presence of the queueing candidate being serviced at a particular counter or particular type of counter”.
A staged queue is quite common in a hospital flow, where there is a cash queue, then a general tests and check up queue, then there is a reports collection queue, and then there is a doctor consultation queue, and then if there is a recommendation for another consultation or another test in the same premises, the patient would need to queue up again for the recommended consultant and tests, of course going through the cash queue again.
Another typical example is that of a walk-in job interview queue or an audition queue. Where the candidate may go through multiple rounds or interviews conducted by a hierarchy of panelists.
Slow Moving Queue
Examples of slow moving queues are: dentist's queue, salon's queue, etc. Typically when there is a human service provider, and is skilled, and who attends to only 1 person at a time, the service time would go up. Even a queue of 12 people would force the last person in the queue to wait for 3 hours if the average consultation time is 15 minutes.
Fast Moving Queue
Sometimes, increasing the service counters is not feasible, so the speed at which the counter is relinquished would typically control the queue length. Moreover, even if the service counters are increased, the number of people in the queueing environment would not change, so space constraint problems can not be solved by increasing the number of counters. An example of fast moving queue is queue of voters. Another example is queues that build up at office gates, where the only action is to swipe the card. Another example is queue for access to coffee machines.
Examples of batched queues can be seen at popular places of worship or at tourist destinations, where the gates would open for a batch of say 100 people to enter and then shut down, until approximately 100 people exit out from the exit gate. This is done to ensure that there is no over crowding inside the tourist place or at the place of worship.