How a picture of a fly reduced washroom cleaning costs by 8%

Intervention · Health


Men’s lack of precision when aiming into the toilet increases the cleaning costs of public washrooms; Amsterdam’s Schiphol Airport was no exception.1 The airport wanted to improve urinal aim to reduce total cleaning costs. As a simple and inexpensive way to achieve such goals, Schiphol Airport introduced its urinal flies.

By etching an image of a fly inside every urinal, Schiphol Airport hoped to nudge men to aim at the fly improving overall aim.1 Implementing this physical design change reduced spillage by 80%, and the budget for cleaning public toilets by 8%.


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Rating = 3/5 (Easy to implement, data collection methods could be improved)

How Fly-Stickers Reduced Spillage and Cleaning Costs at Schiphol Airport
Absence of fly decals Pre-intervention measurements were not provided. 
Fly decals An estimated 50-80% reduction in spillage and 8% in cost

The Nudge: A small fly decal placed in the bowl of each urinal

fly image in urinal

Key Concepts

Nudges: Techniques to change people’s behaviors in predictable ways without forbidding any options or significantly changing economic incentives.

Physical design change: A type of nudge that focuses on changing the physical environment to facilitate performance of a desired behavior or to create barriers for an undesired behavior. 

The Problem

Urinal designers have long been interested in finding a solution to the issue of splashback, a result of poor precision when aiming into a toilet bowl.1 Urine is acidic, so splashback can damage surface appearances.2 Urine can also draw soils and dust to it while wet, accumulating on floors and walls, which allows the areas to house bacteria and other pathogens. Overall, splashback presents a difficult challenge for custodial teams working in public spaces, which is amplified when poor aim results in direct spillage. Plus, we’re all familiar with the smell.


The whimsical world of urinal flies

The “urinal fly” is exactly what it sounds like: the image of a small fly is etched into the urinal bowl.1 All urinals in the Schiphol Airport had the fly in the same position, just above the drain and skewed to the left. (People familiar with this design have noted that it doesn’t necessarily have to be a fly—users would direct their urine at other images too.) 

The urinal fly was introduced by Aad Kieboom and suggested by Jos van Bedaf, who was the manager of the cleaning department.1 Van Bedaf was first exposed to urinal targets while in the army in the 1960s. His experience with physical design change, specifically in the context of urinal aim, caught the attention of management. After that, it wasn’t difficult to get approval for urinal flies and move forward with the project.

Why a fly?

If you think that seeing a fly would evoke unsanitary images, you’re not alone.1 In fact, that’s what typically comes to mind for the individuals who visit the washroom. However, people are more likely to aim at something they dislike. If the fly was replaced with a delicate image (i.e. a butterfly), users may feel guilty aiming at it. If the fly was replaced with a scary image (i.e. a cockroach), users might get scared and avoid the urinal altogether. The fly is a compromise: it’s universally disliked but it doesn’t elicit fear, nudging users to aim at it and thus reduce splashback.

The behavior change framework

Schiphol Airport’s urinal fly exemplifies the SaniFOAM framework, which emphasizes focus, opportunity, ability, and motivation in the context of sanitation.3

  • F(ocus): Urinal flies make explicit the specific behaviors (urinal aim) and the  populations being targeted (individuals who visit Schiphol Airport washrooms with urinals).
  • O(pportunity): This nudge is easily visible, due to the dark fly being contrasted against an otherwise clear, white canvas. So, urinal users have the opportunity to change their behavior.
  • A(bility): Individuals using standing urinals (hopefully) have the necessary knowledge to direct their aim. While urinal aim may be a barrier for some, such individuals could use more accessible facilities.
  • M(otivation): Users have nothing to lose by directing their aim at the fly; the physical design change just implicitly motivates them into changing their behavior.

Results and Application


Schiphol Airport’s urinal files can easily be implemented into any public or private washroom. In fact, there is now a website that creates and delivers a host of urinal stickers, including a fly decal.

Its true effectiveness remains unknown

In terms of effectiveness, it is unclear exactly how much the fly targets reduce cleaning needs.1 Some claim it can reduce splashback by up to 80%, and Sphinx, Schiphol Airport’s urinal manufacturer, says that the fly has led to savings in cleaning costs by a minimum of 20%. Schiphol Airport is often cited as the source for studies on spillage reduction, but no studies have been conducted to corroborate these results. 

All effectiveness rates have been based on observational estimates, with no testing methods. Kieboom estimates that the savings in cleaning costs are closer to 8% – rather than 20% – assuming the 80% spillage reduction is accurate. This is because the total public washroom space that requires cleaning can be divided into approximately 20% for general spaces, 40% for men’s rooms and 40% for women’s rooms. Of the men’s 40%, a maximum of 25% is reserved for urinals, which ends up being only 10% of total public washroom space. 

So, while the intervention is cheap and widely applied, its effectiveness might be lower than initially advertised.

Health & Wellbeing Similar nudges might be used to decrease other unsanitary behaviors, e.g., not washing hands after leaving the washroom.
Development and Social Protection Some studies suggest that images of moral leads can help employees protect themselves from unethical requests, by nudging employers away from issuing them in the first place.  


  • While the intervention was effective, its effectiveness might be overstated.
  • Participant autonomy was preserved.
  • Data was collected without tracking individual participants, so it is unclear how consent and privacy were secured.

Does the intervention demonstrably improve the lives of those affected by it?
Room for Improvement
While it is plausible to think that the intervention was effective, its results have yet to be double-checked, and there is some reason to think its initial effectiveness was overstated.
Does the intervention respect the privacy (including the privacy of identity) of those it affects?
Insufficient Information
It is unclear if privacy was respected, since data collection did not involve tracking any individual’s washroom habits.
Does the intervention have a plan to monitor the safety, effectiveness, and validity of the intervention?
Room for Improvement
While effectiveness was measured, there is some reason to doubt them.  Additionally, it is unclear if there was a plan to monitor participant safety, and the intervention’s validity.

Does the intervention abide by a reasonable degree of consent?
Insufficient Information
It is unclear if consent was gathered, since data  collection did not involve tracking any individual’s washroom habits.
Does the intervention respect the ability of those it affects to make their own decisions?
Participants were allowed to choose whether they tried to target the urinal fly.
Does the intervention increase the number of choices available to those it affects?
Not Applicable
The number of choices stayed the same: to splash, or not to splash. 

Does the intervention acknowledge the perspectives, interests, and preferences of everyone it affects, including traditionally marginalized groups?
Insufficient Information
The intervention does not discuss how it extends to individuals who can’t properly use urinals, e.g., because of a disability. While it can be assumed that such individuals might opt to use a different facility, this is not explicitly discussed or measured.
Are the participants diverse?
Insufficient Information
Data was not tracked at an individual level, and we do not know Schiphol Airport’s demographics.So, the diversity of the participant set is unclear.
Does the intervention help ensure a just, equitable distribution of welfare?
Many cleaning products are not environmentally friendly, and climate change disproportionately affects traditionally underserved groups - reducing their use could be said indirectly promote equity.

Related TDL Content

Evidence based strategies for washing your hands

Urinal splashback is not the only sanitation issue in public washrooms. Another common issue is that some people often leave the washroom without washing their hands. In this piece, Karine Lacroix documents how another behavior change framework, EAST, can increase hand washing in public spaces.

Promoting public sanitation and gender equality by leveraging behavioral insights

Men’s urinal aim is far from being the only aspect of public sanitation that can be targeted by behavioral science strategies. The Decision Lab was recently approached by Aerosan and the Government of Nepal to promote better sanitation practices, particularly as it relates to gendered public toilet access. Request our case study if you’re interested in learning how we were able to help!


  1. Evans-Pritchard, B. (2013). Aiming to reduce cleaning costs. Works That Work.
  2. Waterless Co. Inc. (2016, November 23). Why facility managers need to know about urinal splash back.
  3. Flanagan, A. E., & Tanner, J. C. (2016). A framework for evaluating behavior change in international development operations (IEG Working Paper 2016/No. 2). Independent Evaluation Group.
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