What's the point of hi viz?

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  • http://www.roadsafetygb.org.uk/news/5982­.html

    Worrying report.
    Hi viz good or bad?

    Red herring perhaps?

  • What's worrying me is how out-of-focus that @MultiGrooves guy in the photo is... was the photographer temporarily blinded by dayglo?

  • More of a neon yellow herring though, right?

    I like to ride a brightly painted bike, and have good lights that are visible in daylight on most of my bikes. Then I can wear what the fuck I like.

  • Bizzarly yes .
    Never seen him in hi viz before

  • You looked very dapper this morning skülly

  • Looks like selection bias. If you read the way people had been recruited to take part it appears all had an interest in obtaining a free high vis jacket and so it's likely that they would disproportionately see the jackets as useful and ride/report/influence in a way that would give skewed data.

    In total, 11,202 cyclists signed up for the study. Only cyclists who would ride their bicycle at least three times a week in the summer and who were at least 18 years old when signing up were recruited. 366 registrations were rejected because they failed to meet the criteria, see Fig. 2. The cyclists were stratified on the jacket size (S-XXXL) since the jackets were produced in advance and therefore limited in amount. Thus, not all cyclists who signed up were selected to participate. 8042 participants were randomly assigned to the test and control groups. Of these, 6793 participants confirmed their participation (test group, n = 3402, control group, n = 3391). The test group participants received the yellow bicycle jacket to wear during the study period, while the control group used their regular bicycle garments with the prospect of receiving a yellow bicycle jacket after the completion of the study.

    And then.

    When signing up for the study, participants completed a web-based questionnaire containing demographic information: subject characteristics (gender, age), car ownership (yes/no), bicycle riding frequency (intervals) and jacket size needed.

    To further skew the data collected one group receives the reward for joining and one at the end for participating during the reporting period. It's in the interest of those without a high vis jacket to continue participation and interaction via reporting incidents as that would result in a high vis jacket at the end, for the group who has been given them at the start they have a different lower level of incentive to continue participation.

    Only issue I can see is that the voices who shout loudly for more high vis will champion it's results and it's so wordy most won't look beyond the sensational headline of it.

  • That was for the maiden ride/opening of CS...whatever the number from Clapham ini=to the City. The then mayor, boris was meant to be on that but didn't in the end.

  • Thanks @clockwise good start to debunking this report. Any other ideas?

  • Well, reports like this have been around for ages, as have reports coming to the opposite conclusions, just like with helmets. I wouldn't trust them.

    The desire to impose a requirement for hi-viz on cyclists is, as ever, part of the desire to transfer responsibility from the driver of a motor vehicle (equipped with very bright headlights whose main relevant effect is to increase driving speed at night) to a cyclist, who would most likely be the victim in the event of a collision.

    It's intensely boring how it keeps happening over and over again.

  • Bravo, well said^.

  • I'm guessing this would be disagreed with but as a rider of a bike, I would rather take responsibility of myself entirely and not transfer it on to anyone else. thats just an accident waiting to happen

  • It's intensely boring how it keeps happening over and over again.

    Indeed and demonstrates depressingly little shift in moving away from the motor centric society we live in despite compelling reasons to do so.

  • I would rather take responsibility of myself entirely and not transfer it on to anyone else

    Ah so you're planning to, or have undertaken some cycle skills training
    Good show!

  • Hi viz isn't my shade, brings out my witchy undertones.

  • How far do you want to dig?

    If you could get hold of the questionnaires and all other material the participants had you could tell if it was full of leading questions and statements about high vis that sway the participant. The most obvious one on that front is that those who respond to say they have had a crash are given another longer more effort inducing task of filling out a form. It's a great trick for getting less negative feedback if you threaten negative feedback with a further form, obviously if your participants view filling in that further form as a positive(proof to show high vis works/is needed) then it is more appealing and skews the results. It's difficult to actually make something that isn't bias which is why when studying statistics it takes up such a huge chunk of it.

    Just thinking from work how do you think feedback would come in if you put out this questionnaire.


    Good instructors wear helmets and high vis, based only on your session rate your instructor between 1 and 10?(If 1-3 you will be asked to fill in a further 7 page form to explore why you felt this)
    Comments on your instructor?
    [text box]


    I'm guessing as I've made that question bias lots will score the instructor lower(if not wearing helmet+high vis) followed by a comment about what they had been wearing but as I've said 1-3 will need more effort loads will pick 4/10. To further make that worse if I've set it up in the right way to push my bias more I can use the ambiguous feedback in the text box to further influence score the way I want.

    The same would be true if they started questions saying "high vis is well known to help with crashes..." or any other wording that places an idea out like that.

    If you look at the image of how they have spread out the participants you can also call into question if the participants had been equally exposed to risk with a disproportionate amount in one group in greater proximity to a higher risk urban environment. They have recorded in 2.2 a number of things but not proximity to urban enviroments or any real details of the nature of the cycling taking place beyond that they excluded mountain bike riding, this omission can have a vast impact on results. Not something I ever figured I'd get to say but it's the gerrymandering of high vis studies.



    Had to make the most of that, I doubt I'll get to say it again soon.

    If you don't understand gerrymandering watch this.


  • oh yes, motorbike training. and cycling proficiency when I was a nipper.

    makes me a right know it all. see plenty of horrendous riding (seems to correlate with hi-viz...) and get this, never had an issue on the road. had a few "would have been bad" situations, but saw it coming a mile off and it didn't come close to happening.

    everyone should do it

  • It might be worth seeking cycle training again, in the same way driving skills have moved on and some driving practices have been changed entirely cycling is much the same. Motorcycling experience does undoubtedly increase a cyclists ability to identify some risks but at the same time some risks posed to cyclists are not risks to motorcyclists and so aren't identified. We all spot bad riding and driving, it's good you are open to the idea of training delivered by professionals to correct any bad habits you might be unaware you have.

  • yeah would be open to that, I've done a refresher course for the motorbike once and considered car soon. did a bit of aim stuff for driving but it was a long while ago.

    can you give an example within say the last 10 years of new practice for bikes?

  • I've not been teaching 10 years to put a date on it, I'll also very openly say that even now a number of different sources claim to offer cycling advice and to some degree services people mistake as training tho they are not always qualified to deliver such training or are presenting something that isn't training so others think it is training. Even this for example while I'm qualified to deliver training I wouldn't say us talking on a forum has trained you or made you my trainee at all, what I type is by our human nature ambiguous in places and I can't ascertain your level of understanding or application to other riding situations you might face.

    The old advice for "cycling proficiency" when turning out of a side road would place you at the sides allowing a driver to come up alongside you and even overtake at a junction, what is taught now places you in the middle of the lane minimising the chances a driver can come up alongside you and overtake in that way.

    Just look at this old televised cycling proficiency clip, the riding of the obviously bad rider is still obviously bad but the position of the "good" rider making that left turn in round one potentially exposes them to what many regard as extremely high risk especially if involving large vehicles.


    And yes the riding in that video continues striking all the wrong cords.

    I think we are also getting rather far from the talk about the high vis study.

  • Obviously high viz is a red herring. We need to concentrate on the real problem. You can wear all the bright neon you want, if people don't care to look, there is no use. When I cycle my bright pink cargo bike in winter, adorned with flashing neon lights (as you do), I still get smidsy. Is that because I didn't make myself "visible", or is that because drivers are not paying attention?

  • Also, perhaps as a sidenote: this study was held in Denmark. A country were high viz is a lot less prevalent than in the UK. Could it be that Danes subconsciencely think "whoaaa high viz, something is wrong/up, I need to pay extra care", whereas their uk counterpart is more blinded by it because high viz is now so common they don't really see it as a warning sign? No studies, as far as I know have been made around this. Also, how can you compare the two countries when one country is pretty much only known for decent cycle infra?

  • The last thing I read I was that reflective strips made no difference in the day. A brighter colour or flouro did make riders more visible, However the difference was very minor.
    The significant factor was the reflective strip were substantially more effective at night. Colour was irrelevant.

  • I'd rather be run over than wear a high viz. I have enough of them on me all day at work.

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What's the point of hi viz?

Posted by Avatar for skydancer @skydancer