Is Stopping at Red Lights Bad for You?

red light science blog

The road ahead of you is free-flowing finally! You get passed all that traffic and are finally moving at a good pace. As you come up to the intersection, the light turns yellow. The car ahead of you stops, and if your in New Jersey, you honk because it was clear both of you could have made it through. None-the-less, you are stopped at this red light and it is pretty annoying. But what if I told you it was also bad for your health to be stopped at this light?

A University of Surrey study found that drivers stopped at traffic lights are “exposed to harmful nanoparticles” while stopped at a traffic light. These nanoparticles are being released by the vehicles at the lights. According to the study, approximately 25% of the time drivers are exposed to these nanoparticles, they are at traffic lights. However, they are only at traffic lights 2% of the time they spend driving. That is a significant amount of exposure for an occurrence that only happens 1/50 of the time one spends driving.

So will keeping the windows shut or turning off the fan keep the amount of exposure to these harmful nanoparticles down? The study tested this theory with an experimental trial featuring a control group where the windows were wide open (See Table: Set 1). The trial also featured groups where the windows were shut, but with the fan slightly on with the heat (Set 2) and fully on (Set 3). Another group featured the windows shut with the heat on (Set 4).The last group featured the windows shut and the fans off (Set 5).

Table A explains the Particle Number Size Distribution (PND) which is the exposure to the nanoparticles in each setting. Set 1 is clearly the most exposure, whether it is morning or evening, with the windows down. Using both heat and fan in Set 2 also created more exposure than the other choices. Using the fan and heat individually in Set 3 and Set 4, respectively, created slightly less exposure than the previous settings. The least exposure during the settings was Set 5 with windows up with the fans and heat off.

Table from the University of Surrey Study on

(a) In–cabin PNDs for Set1, Set2, Set3, Set4 and Set5, respectively. (b) Outside ...

This study, even though it is individual, does indicate the nanoparticles are least harmful at traffic lights if the windows are shut with the fans and heat off. The exposure was least in this case. There are not other studies to compare with this studies results or do a meta-analysis on, but the well-done nature of the experimental trial makes its findings somewhat trustworthy. Based on the results, it appears stopping at traffic lights is harmful and it is wise to keep the windows shut with the fans/heat off when stopped at a red light or avoid intersections as much as possible.


5 thoughts on “Is Stopping at Red Lights Bad for You?

  1. Margaret Kreienberg

    While this is a very interesting article, I still do not see the danger in stopping at a red light. Set 5 had the least exposure to these particles. Set 5 is actually most similar to the conditions that I drive under. Since spending time as a red light only lasts a few minutes at most, I really do not see the harm. What is the hazard? How harmful are the nanoparticles? The exposure is very low. Because of this, the risk might not be as high as you think. Also, while the results seem reliable, it is only one study. Many studies should be conducted to see if the results of this study actually hold true. There is not enough information to draw a valid, firm conclusion.

  2. Kelsey Donehower

    I never would have thought that safely being stopped at a red light was bad for you. You are probably the safest in the car when you are stopped at a red light, or at least that is what I thought. This post was extremely fascinating and will definitely affect how I sit at a red light. I thought it was interesting how there was an actual study done on this and I liked how you included charts. I found this article that agrees with everything you said and it also said a way to lower the exposure to these particles is by keeping a distance between your car and the car in front of you. Really awesome post!

  3. Madisen Lee Zaykowski

    I’m curious as to how you thought of this topic! it was different thanI first expected it was going to be, and never thought about something so little having any repercussions because we all know to stop at red lights. Out of curiosity, I found a website that further explained nanoparticles, and what other purposes they could be used for called “Nanoparticle Applications and Uses. “ It was interesting too read about how they can be used in medicines and in other things we use throughout the day, like electronics. Nevertheless, I am glad that I now know some tips to avoid exposure to the negative nanoparticles when stopped at a stop light.

  4. Daniel Liam Cavanaugh

    Before reading this blog, I tried to think of a reason for how red lights could be bad for you, but couldn’t come up with anything. What you proposed definitely makes sense and is enough for me to be watchful for it in the future. I have some questions, though. Are these nanoparticles released with the gas from cars? What is harmful about these nanoparticles? How do they affect us? Are traffic lights the most dangerous places to be in terms of nanoparticle exposure? If you want to further your research into this topic, here’s another source: For your next blog, a similar, interesting topic would be to discuss carbon monoxide emissions from cars. It seems like carbon monoxide exposure inside cars may be higher than we realize. A blog on this topic would be very informative. Here’s a source if you’re interested.

  5. Elyssa Paige Woods

    This is a topic that I have never given much though about. When doing some research I found that the part that causes the most health issues is when the light goes from red to green and a car has to “rev” its engine to start up again. This is when most of the nanoparticles are released causing health concern. What I would like to know though is a solution to this problem? It is not like the whole world can get rid of red lights and traffic jams. This is something to think about if you or anyone else were to do more research on this topic. Overall, really interesting topic choice!

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