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Only If They Think They Can Get Away with It?

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How many times have you seen a car without the appropriate permit (either a license plate or placard that hangs from the rearview mirror) parked in an accessible parking space reserved for people with disabilities? If you find this behavior upsetting, you might be interested in figuring out how to discourage "cheaters" who use these spaces to make a quick trip into the store. Is it enough to let them know someone might be watching?


Areas of Science
Time Required
Average (6-10 days)
Material Availability
Readily available
Very Low (under $20)
Adult supervision is required.
Andrew Olson, PhD, Science Buddies
Thanks to Science Buddies alumnus Courtney Corda for the project idea.



The goal of this project is to find out if abuse of accessible parking spaces decreases if drivers are aware that they are being monitored.


Have you ever watched the accessible parking spaces reserved for people with disabilities and wondered how many people are using them legitimately? Most states require drivers with disabilities to have either a special license plate or placard that hangs from their rearview mirror (typically with a "wheelchair" symbol) to indicate that they can legally use the parking space. Do you ever see a car parked in an accessible spot without the appropriate permit? Here is an idea for an experiment you might try to see what factors can change accessible parking behavior.

The idea is to start by gathering a baseline sample by observing the normal usage of accessible parking spaces at a busy parking lot. Determine the total number of cars that use the spots, and how many of the cars have the appropriate permit for using the spots.

Next, put up a sign with a message to deter cheaters from using the spots. For example, the sign could say: "These parking spaces are being observed today as part of a science fair project. Please use these spaces only if you have an appropriate disability parking tag." Gather a second sample by observing the accessible parking spaces as you did before. If multiple languages are commonly spoken in your area, you may want to consider making a bilingual or multilingual sign. In this case, choose the two or three languages most commonly spoken in your area.

Important: Note that some drivers may have a disability, such as a heart or lung condition, that is not clearly visible. For this project, you should only evaluate whether or not the car parked in the space has the appropriate tag or license, not whether the person driving the car "looks" like they have a disability. We do not suggest making any attempt to survey the users of the accessible parking spaces. This is an observation-only study.

Do you think that placement of a sign informing drivers that the parking spots are being observed will have a deterrent effect on cheaters?

Terms and Concepts

To do this project, you should do research that enables you to understand the following terms and concepts: Questions


  • Wikipedia Contributors. (2006, October 8). Deterrence (psychology). Wikipedia: The Free Encyclopedia. Retrieved February 2, 2007.
  • Bergal, J. (2014, November 17). States Cracking Down On Accessible Parking Abuse. Disability Scoop: The Premier Source for Developmental Disability News. Retrieved April 6, 2015.
  • For a detailed study on parking enforcement policy, see this report from the British House of Commons (there is a section on 'Blue-badge' parking beginning on page 69):
    House of Commons Transport Committee. (2006). Parking Policy and Enforcement. Retrieved February 2, 2007.

Materials and Equipment

To do this experiment, you will need the following materials and equipment:

Experimental Procedure

Working with Human Test Subjects

There are special considerations when designing an experiment involving human subjects. Fairs affiliated with Intel International Science and Engineering Fair (ISEF) often require an Informed Consent Form (permission sheet) for every participant who is questioned. Consult the rules and regulations of the science fair that you are entering, prior to performing experiments or surveys. Please refer to the Science Buddies documents Projects Involving Human Subjects and Scientific Review Committee for additional important requirements. If you are working with minors, you must get advance permission from the children's parents or guardians (and teachers if you are performing the test while they are in school) to make sure that it is all right for the children to participate in the science fair project. Here are suggested guidelines for obtaining permission for working with minors:

  1. Write a clear description of your science fair project, what you are studying, and what you hope to learn. Include how the child will be tested. Include a paragraph where you get a parent's or guardian's and/or teacher's signature.
  2. Print out as many copies as you need for each child you will be surveying.
  3. Pass out the permission sheet to the children or to the teachers of the children to give to the parents. You must have permission for all the children in order to be able to use them as test subjects.
  1. Important: Before you get started, please note the following precautions:
    1. Many busy parking lots are located on private property. Before you start your observations, be sure to obtain permission to conduct your study from the property owner and/or manager. Get an adult to help you if necessary.
    2. Some cities or states may have laws that prevent you from hanging additional signage on the signs indicating accessible parking spaces (or other street/parking signs for that matter). Have an adult help you check to make sure that you are not violating any local laws when doing this project.
    3. Remember that your science fair may have specific requirements regarding experiments with human subjects, especially if the subjects do not know they are being observed. Check with your science teacher or fair organizer to see if it will be okay to do this project. See the links at the beginning of the procedure for more information.
    4. Avoid confrontations with drivers. Remember that some drivers may have a disability that is not easily visible, like a heart or lung condition. You should not accuse anyone of "cheating" when using an accessible parking space. For safety, have an adult accompany you while making your observations.
  2. Select a frequently used parking lot with clearly designated accessible parking spaces.
  3. Observe usage of the reserved accessible parking spaces for enough time to collect a representative baseline sample.
    1. The amount of time required will depend on how frequently the spaces are used.
    2. To determine how many observations you need to make in order to have a reliable sample, see the Science Buddies resource Sample Size: How Many Survey Participants Do I Need?
  4. For each car that uses a space reserved for accessible parking, mark down whether or not the car has the appropriate placard or plate to park in the space in your lab notebook:

    No disability placard or plate Has disability placard or plate

  5. After you have collected your baseline sample, place your sign(s) in a clearly visible location near the accessible spaces. Collect a second sample and record your data in your lab notebook.
  6. From your data, calculate the following:
    1. Total number of cars parked
    2. Total number in each category
    3. Percentage of cars in each category
  7. Does the percentages of cheaters decrease when drivers are being observed?
  8. More-advanced students should determine the statistical significance of any changes with a t-test.
icon scientific method

Ask an Expert

Do you have specific questions about your science project? Our team of volunteer scientists can help. Our Experts won't do the work for you, but they will make suggestions, offer guidance, and help you troubleshoot.


  • Compare the effectiveness of different messages on the sign. For example, try "Thank you for not using the accessible parking space when you are not eligible!" (reward) vs. "This accessible parking space is being monitored today." (deterrent).
  • Try pitching your project with your local police department and see if you can get their cooperation for a third phase of your project. Pair the deterrent sign with a squad car parked right next to the accessible spaces and observe another sample of drivers. Deterrence is supposed to work better when there is a higher probability of being caught. Does the presence of the squad car affect the results?
  • How long does deterrence last? If your sign does decrease the percentage of violators, keep checking back over the next several days to see if the cheating rate returns to baseline.
  • Your local newspaper might be interested in your project. If they print an article on your project, does the additional publicity cause a lasting deterrent effect?
  • Can you come up with an estimate of how frequently people abuse the acessible spaces as a percentage of total parking lot use? Design a study to find out.


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General citation information is provided here. Be sure to check the formatting, including capitalization, for the method you are using and update your citation, as needed.

MLA Style

Science Buddies Staff. "Only If They Think They Can Get Away with It?" Science Buddies, 20 Nov. 2020, https://www.sciencebuddies.org/science-fair-projects/project-ideas/Soc_p013/sociology/perceptions-behavior. Accessed 30 May 2023.

APA Style

Science Buddies Staff. (2020, November 20). Only If They Think They Can Get Away with It? Retrieved from https://www.sciencebuddies.org/science-fair-projects/project-ideas/Soc_p013/sociology/perceptions-behavior

Last edit date: 2020-11-20
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