Are there any studies on the effect of helmets and/or other impressions of the bike rider, on driver behaviour?

Has anyone collected their own data on things like this?

Has anyone noticed any other slightly unexpected oddities like the two I observed bellow?

Recently I had to ride back home on a road down a 10km route which I've travelled many times before, but without a helmet, the difference in driver behaviour was very noticeable... I got a lot more space, didn't have a single car overtake me dangerously close (though a few were certainly still illegally close).

I've noticed similar differences when i'm sort of practising riding skinnies by staying dead in the middle of the lines at the sides of roads (this seems to give drivers FAR too much confidence to act dangerously... I was already worried about this particular test after just one day, I was actually interested in getting hard data riding on the lines vs normally vs unstable and wobbly (against number of cars coming dangerously close (based on video)) unfortunately i only got as far as anecdotal evidence that skinny practice on road lines is dangerous as hell, that normal riding seems much safer and that wobbling about unstably does seem to make you safer from drivers, but it's easy to get carried away. Then as I was practicing skinnies some twatwaffle hit me with his wing mirror, putting me off balance, scaring the shit out of me, and ending my desire to gather data, while increasing my desire to keep away from asphalt in general.

Those experiments ended, and I never thought about it much till the helmet incident recently... I'm certainly not intending to do the no helmet experiment myself, so I was wondering is there any real data for this kind of thing, or any other interesting phenomenons to do with driver and cyclist etc?

  • I can only say that me as a cyclist feel safer wearing a helmet, and that this feeling of safety is probably ill founded, I should feel as naked and fragile as when I ride helmetless, because I never want to get hit among traffic, be it wearing a helmet or not.
    – gaurwraith
    Dec 10, 2017 at 12:32
  • I feel safer without a helmet on the road, with in the woods, I'll go without a helmet without a second thought on the fire-roads for transport in the day time. At night time I do worry about a random boar or deer causing an accident. Undecided on overall worth, but probably slightly better off wearing one everywhere... except the rotational stuff and the fact that MIPS isn't really much good at it... maybe i'm just buying into conformity.
    – user20209
    Dec 10, 2017 at 12:58
  • 1
    Anecdotes aren't good answers when statistics matter hence why this is a comment, but looking wide makes a big difference (e.g. riding with a wheel strapped to my back). A child seat increases most drivers' pushinge distance but not the closest. Switching from a baby seat to one where the child is more obvious and with wide foot rests (and lights on the end of the foot rests) did make a difference. Drivers generally don't want to hit you (it might scratch the paint) but many are clueless as to width.
    – Chris H
    Dec 10, 2017 at 19:20
  • Funny I had this thought re: Criggies answer, after I went to the guys website to download the original data and saw that he was doing the test with commute bag things on the back of the bike, and wondered if that would affect the outcome... incidentally the I also recall no one got anywhere near me at all was when I was carrying a 90x60 cm painting under my arm :)
    – user20209
    Dec 11, 2017 at 3:30

3 Answers 3


Seems there are studies showing both:

2008 Walker study - "Cars get closer to cyclists wearing helmets"

when Walker wore a helmet drivers typically drove an average of 3.35 inches closer to his bike than when his noggin wasn't covered.

However in https://helmets.org/walkerstudy.htm in 2013 this was refuted. Also https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3783373/

After re-analysis of Walker's data (2006), helmet wearing is not associated with close motor vehicle passing. The results, however, highlight other more important factors that may inform effective bicycle safety strategies.

I don't have my own data, merely subjective anectodes about how much room I receive when riding a tandem, or towing a 2-wheel trailer, or the two times I trialled a recumbent and had cars crossing the road to go around me. I'm NOT that wide.

Locally, milk tanker drivers are awesome at passing with extreme room. They don't slow down from their permitted maximum of 90 km/h but they will give me a full lane of passing space where possible, which is 5-6 metres.

  • 1
    Hmm had a look through the study and refutation, not entirely convinced by either. Furthermore I think it's far more important to measure what proportion get dangerously close (for me that would be 50 centimeters or so, though I don't feel particularly comfortable with less than 1 meter) I found this interesting in the refutation: "laypersons have used Walker's findings to justify the removal of mandatory helmet laws [15], [16]." This is amusing because there are far better arguments and data to push against mandatory helmet laws.
    – user20209
    Dec 10, 2017 at 11:23
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    My observations were mainly that sans helmet a few more cars go wide++, and almost none get dangerously close, also the wing mirror clipping I got was on a narrow part of the road where I don't normally get overtaken, pretty sure the guy wouldn't evne consider overtaking if I was another half metere out into the road (forced well into other lane to do it)... interesting that the original study concluded the opposite effect occurs, but I wonder if his relatively obviously wide bike (satchels) vs my seemingly narrow general use MTB bike with 780mm bar plays a role here...
    – user20209
    Dec 10, 2017 at 12:10
  • 2
    The authors acknowledge some concerns, e.g. the need for retreating room (my term). They're working on other topics now (I missed a talk distantly related to some of my own work by Walker, that was apparently very good). Wing mirror clipping is so rare as to be an outlier, and so it's very hard to assess statistics
    – Chris H
    Dec 10, 2017 at 19:23
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    Perhaps time to take this extended discussion over to chat and leave comments to clarify the answer.
    – mattnz
    Dec 11, 2017 at 0:16
  • that is great that you are given that much space! most of accidents happen when car hit the bike on overtake.
    – kifli
    Dec 11, 2017 at 11:23

If the cars have lights on, I feel somehow better respected when I have lights on too (red at back and white at front, not flashing, brightness and angle adjusted reasonably). This is often that would be called a day (rain, morning, evening, fog, etc).


More info: Cycling helmets: do we need them?


Listen: http://www.radionz.co.nz/national/programmes/sunday/audio/2018618841/cycling-helmets-do-we-actually-need-them

  • 4
    Welcome to SE - we generally dislike link-only answers because they become useless when the link changes. It would be better to state the main points in your answer, and leave the links as extended information. Specifically focus on the question being about "driver behaviour" and not generally about helmets. Do have a browse through the tour to see how SE is a bit different to a common chat website. As a fellow kiwi, we're an example to the rest of the world about how mandatory helmets have affected cycling culture, both for the better and the worse.
    – Criggie
    Dec 14, 2017 at 4:00

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