Public restroom design

Queuing Theory And The Design Of Public Restroom

| Washrooms & Beyond


Queuing Theory and the Design of Public Restroom

Queuing theory is used to analysis of public toilets /restroom use and behaviour. It is also used to examine the problem of long waiting lines at women’s restrooms. The structure of the theory is explained with respect to the factors which are most likely to affect the service rate and their implication design, and management is discussed in detail.

Analysis of the design problem of long wait up lines at women’s public restrooms through the use of this theory provides greater insight into the problem. The results contributing to an optimal design in collaboration with the management are achieved.

The Problem

Women often experience having to stand in long lines in order to use public toilets/restrooms men can be overhead asking “what took you so long?”. Long waiting lines are common for women in festivities like airports, conference centres, highway restrooms, sports centres, theatres, and concert halls during intermission. The consequences include inconvenience, health concerns and emotional concerns (anger, resentment, frustration). There is growing awareness of this problem and to increase in the number of fixtures in the public toilets/restrooms for women.

There is growing public awareness of the problem of elimination fixture inequity in women’s restrooms. Early on, the queuing theory was applied to telephone facilities, later became used for traffic situations, and today is most often used with computers, construction and mining engineering teller windows at banks, and office paper flow. Manufacturing assembly lines and the determination of an optimal number of beds needed in a hospital Intensive Care Unit. “QUEUEING THEORY WAS DEVELOPED TO PROVIDE MODELS TO PREDICT BEHAVIOUR OF SYSTEMS THAT ATTEMPT TO PROVIDE SERVICE FOR RANDOMLY ARISING DEMANDS”. It is the most simplistic form, queuing theory consisting of an unpredictable demand on a system, coupled with the varying amounts of time it takes people to use the system.

Public restroom theory

In this instance, the system is a public restroom. Two situations are presented here and serve to illustrate queuing theory as it is applied to public restroom usage. In the first situation, no matter how quickly one uses the fixture/feature, for example, the water closet, if 50 people are waiting to use the water closet, in all probability, there will be a waiting line. In the second situation, the reverse is true. Even if a person spends a stall, for example, 15 minutes, if there is no demand to use the stall, no waiting line will result. Other factors which must be taken into consideration include (1) queue or service discipline—the order in which users are served; (2) calling population where do the users come from; (3) arrival rate; and (4) service rate. Other factors which can complicate queuing system include: (1) balking; (2) reneging and (3) jockeying. Users are said to balk if they refuse to enter the system because the queue appears too long, and users renege if they leave the system before service, while users jockey if they change queues.

Service Facilities

The number of fixtures and accessories is based on the Plumbing Codes and Design process.

user demand public restrooms

User and facility characteristics

After a lot of investigation and analysis, the user and facility provided for, determine the adequacy of the fixtures & accessories and short cum of the services. It is analyzed by the professionals that the User and Facility characteristics, affect the restroom services.

  • Cleanliness of the Fixtures & Accessories: The problem with cleanliness causes an increase in usage time and often dirtying of the fixtures.  Women’s restrooms tend to have problems with the cleanliness of toilet seats.
  • Maintenance: Condition of the fixtures whether or not in working order and whether the supplies are adequate or depleted.
  • Vanity Counters: Storage place to keep the package, Purse, Briefcase or any other items.
  • Accompanying Child / Children: Persons accompanying Child / Children
  • User Group: Persons in special user groups (i.e. Elderly, Obese, Pregnant). Sufficient fixtures for differently abled to be provided.
  • Age of the User
  • The user is Male or Female


By using the theory, the problem can be analyzed and identified, and the factors which impact the above problems to achieve at the optimum design. Possible design solutions/alternatives proposed by various designers are: –

  • Requiring additional fixtures and accessories
  • Installation of self-sterilizing toilet seats.
  • Self-cleansing wash basins
  • An adequate supply of toilet accessories such as toilet tissues, towels, soap etc.,
  • There is growing public awareness of the problem of an inadequate number of fixtures in the women’s restrooms.
Public restroom planning


On the design of toilet facilities for public buildings, Prof. Mete Demiriz and his colleagues from Germany conducted an extensive study and arrived at new guidelines on plumbing fixtures and accessories for public+ toilets.  They have considered football stadiums as a case study and key factors in their study are;

  • Number of toilet fixtures
  • User Behavior
  • Water Consumption

The measuring equipment were installed in the Ladies and Gents’ toilet to measure the frequency of usage and relative water consumption.    

The data analysed are as follows

  • Water consumption at the washbasin.
  • The number of users and duration of use at the washbasin.
  • The number of users and number of flushing at the urinals.
  • Frequency of cubicle use without locking the door.
  • Frequency of cubicle use with locking the door.
  • Activation of flushing.
  • Intervals in use, frequency of use and simultaneous usage of all sanitary fixtures.
  • Total water consumption and peak flow.


As per existing codes (calculated from international codes)

The fitments require for 1000 spectators in the football stadium are :

public restroom survey results

As per the analysis

Based on the results of the analysis, Prof. Demiriz calculated the results in three different ways considering the simultaneous usage pattern.

public washroom survey results


The new table is based on the assumption that half of the people visiting events are women and half are men. It may be true that women shy away from using public toilets, which would decrease the need for ladies’ toilets, but the time it takes them to use the cubicles for urinating is three to four times longer than it takes men.  On average, women also stay longer at the washbasin than men.  They use the washbasin to put on make-up etc., By means of observations and measurements in football Stadium and assembly places, tables were drawn to help and calculate the appropriate number of sanitary facilities and fixtures.  Prof. Demiriz recommends providing Sanitary Fixtures and accessories as per the table arrived for High-level simultaneous use, also attention was directed to the equality of both genders.


Extracts are taken from the paper published by:

  • K. Rawls. University of Missouri.
  • S. Day. Virginia polytechnic institute and state university.
BSA Narayan

B.S.A Narayan

National Vice President, Indian Plumbing Association, Managing Director, Maple Engg- Design Services (India) Pvt. Ltd., Bangalore

“By using the theory, the problem can be analyzed and identified, and the factors which impact the above problems to achieve at the optimum design.”

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