8

http://www.safetyreflectors.com/education.html has some claims about reflectors:

Studies have proven that the risk of being hit by a motorist in the dark is eight times lower when wearing a safety reflector. The use of reflectors has been shown to increase the visibility of pedestrians by a factor of five. - Federal Highway Administration

I'm suspicious of the site both because it's obviously trying to sell something, and because almost all the talking points are irrelevant. The only thing that matters is how much risk is being reduced by reflectors, so mentioning a bunch of other facts seemed fishy. I also couldn't find the original source of the Federal Highway Administration statement, or any studies that seemed relevant.

So how much risk is actually reduced by wearing reflectors, if any?

(I'd much prefer an answer in terms of miles walked if possible. I'd also like some explanation on how confounders are ruled out; maybe people who wear reflectors are more likely to also be more careful about where they walk and pay attention to their surroundings more or something. There probably haven't been any controlled studies of this for ethical reasons, so I'd really like to know how you can in principle get these numbers. Also, how would they know how often reflectors are used?)

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    I'm mulling whether your restrictions have made the question practically unanswerable. The first sentence about accident rate is only a correlation claim. The FHA sentence about risk of being hit in the dark sounds like correlation claim as well. The final sentence about "a factor of five" is woefully lacking in definitions, but might reasonably have be worked out with a controlled experiment (and, if so, is reasonable to include without it being fishy.) We should be able to test these three claims without reference to your last paragraph. – Oddthinking Feb 5 '15 at 4:31
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    @Oddthinking The first FHA one seemed like a causation claim, and really was the only one that mattered to me if true. "The risk is lower" doesn't sound like correlation to me. The fishiness wasn't from the parts I quoted, but from things like "71 % of fatal adult pedestrian crashes occurred at dusk or dawn or in areas where visibility of the person was restricted." Knowing how much of the accidents were from bad visibility is useless for determining danger, and seemed designed to sway the reader with irrelevant info. – ike Feb 5 '15 at 5:07
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    @Oddthinking The only claim I want to test is the first FHA one about causation, as my title and explanation make clear. I removed the first claim. To test causation, my points in the last paragraph are relevant. (I can try to find a more explicit claim for causation. This is obviously implied, as they're using it to argue you should wear them, which only makes sense if it causes less deaths.) – ike Feb 5 '15 at 5:11
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    Fair enough. I read it as merely a correlation claim, but that's just one opinion. If it is a causation claim, I agree that the last paragraph is relevant - the claim is difficult to prove. – Oddthinking Feb 5 '15 at 5:13
  • The opposite is also possible: that people wearing reflectors have a false sense of security, take higher risks, and that this offsets the enhanced security enhanced visibility should cause. This according a press release by the Swedish college of Skövde. Note that this was about cyclists, not pedestrians. I recall similar claims being made about bicycle helmets. – gerrit Feb 5 '15 at 16:15
7

As of 2004, the answer is "Science does not know."

This conclusion comes from:

This review looked at 1991 potential reports, and selected 29 papers about 37 trials. None of the reports that were found

[quantified] the effect of visibility aids on the occurrence of pedestrian and cyclist-motor vehicle collisions and injuries.

They acknowledged the difficulty in conducting such trials. They noted:

results of the trials do suggest that visibility aids influence drivers' reaction, detection and recognition.

However, they were forced to conclude:

Visibility aids have the potential to improve detection and recognition and would merit further development to gain public acceptance. However, the impact of visibility aids on pedestrian and cyclist safety is unknown and needs to be determined.

Of course, an answer like this is inherently subject to new data coming in and overthrowing it, especially as it was published a decade ago.

  • Can you find the FHA "8 times" claim? Are there any more recent meta-analysis like this? – ike Feb 5 '15 at 5:59
  • Looking through the studies that cite the one you list, I see cycle-helmets.com/norway.pdf, which mentions Erke & Elvik, 2006, as saying "the risk of a pedestrian being fatally injured in an accident where he/she sustains injuries, regardless of severity, is 31% lower when he / she is using reflective materials." – ike Feb 5 '15 at 6:07
  • If your Norwegian is up to reading Erke & Elvik, it sounds like it would make an excellent alternative answer (albeit, probably demonstrating correlation not causation). – Oddthinking Feb 5 '15 at 13:10
2

Although focussed on cyclists and not pedestrians, recent research from the University of Skövde concludes: it depends. The research appears to be ongoing. In 2014, they published a study where they researched what subconscious visual cues determine the intent of cyclists in traffic:

Hemeren, Paul E., Mikael Johannesson, Mikael Lebram, Fredrik Eriksson, Kristoffer Ekman, and Peter Veto. "The use of visual cues to determine the intent of cyclists in traffic." In Cognitive Methods in Situation Awareness and Decision Support (CogSIMA), 2014 IEEE International Inter-Disciplinary Conference on, pp. 47-51. IEEE, 2014.. This appears to be based on a lengthy report in Swedish.

Then, they investigated what visual enhancements help motorists to see this. I haven't found a peer-reviewed study for the second part. All I found specifically for the reflectors is press release in Swedish.

Some cyclists were wearing no reflectors at all, others were wearing some reflectors, and others were wearing reflectors at body places deemed optimal according to previous research. Their conclusion is that it is very important where on the body the reflectors are worn. From the press release:

– Det vi har sett i vår forskning är till exempel att reflexvästen ger en falsk säkerhet nattetid, då den inte på något sätt hjälper bilisten att tolka cyklistens rörelseinformation, säger Paul Hemeren, doktor i kognitionsvetenskap vid Högskolan i Skövde. Sätter man däremot en reflexrand bak på hjälmen, som fortsätter i ett lodrätt streck ner på ryggen, skapar man en linje som bryts av när cyklisten vrider på huvudet. Detta visar att cyklisten med stor sannolikhet ska svänga. Förstärker man dessutom kroppens andra leder med reflexer når man ett ännu bättre resultat. Med vår forskning kan vi påvisa hur man som cyklist kan synas ännu bättre i trafiken. Detta har ingen kartlagt tidigare.

Translation:

What we have seen in our research is that for example a reflective vest gives a false security at night, because it doesn't help motorists to judge the movement information by cyclists, says Paul Hemeren, doktor in cognitive sciences at the University College of Skövde. However, if one puts reflectors on the rear of the helmet, that continues straight down over the back, then one creates a line that breaks when the cyclist turns their head. This shows that the cyclist very likely will turn. If one additionally enhances visibility of other body parts with reflectors, one gets an even better result. With our research we can show how cyclists can be even more visible in traffic. Nobody has systematically looked at this before.

The press release also states:

Resultaten av forskningen är väldigt tydliga. Om reflexerna är placerade så att de förstärker cyklistens omedvetna rörelsemönster gör det att testpersonerna kan göra korrekta bedömningar av cyklistens avsikter i upp till 97 procent av fallen– även nattetid. Helt utan reflexer ligger testpersonernas träffsäkerhet strax över 70 procent.

Translation:

The result of the research is very clear. If the reflectors are placed so that they enhance the cyclist's unconscious movements, the test persons are able to make correct judgements of the cyclist's aims in up to 97% of the cases — including at night. Without reflectors the correct rate is slightly above 70%.

  • This doesn't really answer the question. Even for cyclists it isn't saying whether it reduces risk or by how much. – ike Feb 5 '15 at 18:59
  • Well, I concede that. It would have to be a followup question, but I would consider it reasonable that if motorists make more correct judgements about the cyclist aims, that this would reduce lethal accidents. It remains to be seen if this effect is significant, though. – gerrit Feb 5 '15 at 19:19
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The info is a blending of truth and fiction. Reflectors do increase the visibility profile of a person who is wearing a best or some other such item. The fiction comes in the inclusion of inattentive and distracted drivers.

Imagine being run over by a truck while jogging on a road, while you are wearing the best and clothing with reflective materials. The devices were effective, the was the driver who was texting or watching the game on his device.

Human error is always the unblown factor, and it will always be so. Distracted people are the inevitable dynamic of limitation when it comes to safety.

Some of the information contained in this post requires additional references. Please edit to add citations to reliable sources that support the assertions made here. Unsourced material may be disputed or deleted.

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    This is an opinion, but we only allow answers based on evidence. Can you bring any? – Sklivvz Feb 6 '15 at 9:34
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    It also suffers from the nirvana fallacy. We all agree that reflectors cannot prevent 100% of pedestrian accidents. That doesn't mean they aren't a worthwhile practice, if they can prevent some accidents (which is the question). – Oddthinking Feb 6 '15 at 9:49

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