There has been at least one study done that shows drivers actually give riders less space when passing if they are wearing a helmet or hi vis. Wear whatever makes you feel safe though.

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"Step forward the climber and all those who worship at the altar of lightness" - R. Millar

There could be a disconnect between what is actually safe and what is perceived as safe. In the UK commuting cyclists feel almost pressured to climb into a defensive outfit of helmet, hi-viz clothing and bright lights because that is the public expectation of the outfit that is 'safe' for a cyclist. This attitude can follow through into court cases and insurance settlements.

Whether helmet/hi-viz/lights is truly the best guarantee of safety in all circumstances, who knows.

Yeah, feeling safe while riding and actually riding safely are two things most cyclist do not understand.
Most cyclist will feel safe riding with a helmet, lights, reflective clothing, in a park, or on low traffic road but
that will let their guard down and the probability of making mistakes rises.

In contrast riding safely entails 100% awareness and focus in ones surroundings, the ability to anticipate obstacles and obstructions. The ability to proactively take charge of every situation that comes along. This is regardless of helmets, fluorescent clothing, lights, horns, traffic laws.

Remember, cyclists that ride safely will not put their life into the hands of motorists.

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I never took drugs to improve my performance at any time. I will be willing to stick my finger into a polygraph test if anyone with big media pull wants to take issue. If you buy a signed poster now it will not be tarnished later. --Graeme Obree

...ok, wow.
Who here has actually studied some psychology, physiology (specifically related to vision) and neuroscience? Raise your hand. I have. My whole undergraduate degree is in Psych, actually, and previous to that was pre-med course work.

Hi-Viz is not necessarily the 'safest' method of visibility for objects moving at high velocities.

Why is hi-viz used for construction workers and not their trucks?. Because they aren't moving much by comparison to vehicles.

Now, what do they do for vehicles that are in motion in areas that are extremely hazardous or dangerous?
They add CONTRAST and SHAPES OR PATTERNS which are disjointed from the shape of the object.
Because when those objects are in motion, it becomes obvious due to the contrast and the shape/pattern moving through space.
The color, actually, doesn't make too much of a difference.

A black & white patterned kit will have just as much visibility to the human eye as a hi-viz one when it is placed on an object in motion at some discernable velocity.

A black & white patterned kit will have less visibility than a hi-viz one when the object is in low-speed, minimal activity.

Motion is detected with the RODS in your retina, not the cones, and more importantly through utilizing perceived CONTRAST, not color.
Why do you think the best snipers in the world are color blind? Because they're able to see contrast quicker, no colors to distract their vision.
Why do you think the military (of any country) prefers soldiers who are color blind? Because they can detect movement in even the best camouflage, they are not distracted by color but focus on... guess what... CONTRAST.
Why do you think the world's greatest predators (non-human) see the world in greyscale or black&white? CONTRAST!

Hi-Viz looks cool. It will also help you if you are standing still. Like most construction workers. Who are on break everytime you're within eyesight of them.

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Exp001

Most safety actually is solely upon the decisions of the 'operator' - meaning the cyclist makes the best decisions, to their ability, for their safety.
Riding at night without lights? Not safe.
Riding in the gutter? Not safe.
Riding at night with lights in a dark kit? If there's any contrast to that kit the cyclist might be safe, but if it's all dark colors or solids, it might as well be all black or all hi-viz.

Coincidentally, a lot of "it's safer if you do this vs. that" is psychological... You feel that drivers are nicer to you when you wear hi-viz stuff? Most likely it's down to your own psychological interpretation of a series of events that - so far - have gone favorably, or larger changes to the mindset of drivers towards cyclists.

Remember that old adage that hopefully someone told you at some point in your life?
"The world does not revolve around you."
Guess what? It's still true. Just because you wear hi-viz does not suddenly make the birds chirp, the sun shine, and drivers wave in a friendly manor to you when you're out on the road. Just because you choose to not wear a helmet does not make the world suddenly safer, or change your likelihood of having a crash. The world is much bigger than one individual and operates at a much more intertwined level.

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Exp001

very interesting prefendreu. i´m wondering if a bike at 25km/h is considered a moving object from a car behind at a similar speed... i guess proper bike lanes infrastructure is at the end the best solution...

i recently heard that due the no-noise of electric cars, it's going to increase the number of accidents a lot, as pedestrians and bikers are catch by surprise or just can't hear them with earphones or distracted.

That is correct, velofreak, regarding the increase in quiet cars.

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Exp001

Indeed, when aproaching from behind the cyclist is not a moving object. And being struck from behind is the thing Im afraid the most when riding.

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A light bike does replace good fitness.

...ok, well two things:

1. You have little control over that, no matter what you do. Sorry, that's the truth. Even a re-ward mirror does little good, it will only make you feel better psychologically. If that works for you, use it.

2. Again, CONTRAST. The driver is looking forward at a landscape. Do you contrast with the landscape? Is your kit's pattern distinct from the background? Then you will be seen. Again, color does not make much of a difference. It could be a black & white pattern, it could be a hi-viz pattern, it does not make any difference at all so long as there is a clear contrast to the pattern and it is in contrast with the background (where you are riding)

Just think about it. Heck, go outside and look around you. Notice things that are in motion (even birds!)... It doesn't matter if the object is moving in the same direction as you or not, you will notice if it there is... drumroll please....

CONTRAST!!!!

Easiest example to think of is, sadly, cars. The next time you are driving on a highway and all the cars are moving in the same direction at the same relative speed (ie, no one is speeding through and weaving about), you will notice that the cars that are the *most* visible are the ones with the *most* contrast to the horizon or highway. The grey cars or cars that match the skyline will be the least visible.
Asphalt/Cement is grey? Grey cars less visible.
Horizon blue? Sky-blue cars less visible.
Horizon green with pastures or trees? Green cars less visible.
Cars that are red? Visible... unless the sky is red or the pavement is red... which would be a bad thing and I'd be driving in the other direction if that were the case.
Cars that are any other color? Just as visible as the red cars.
Cars that are white? Medium, average visibility on most average days because they offer average contrast to the environment... nothing startling, but o.k. stuff. In Snowy conditions? Bad of course.
Cars with contrast in them (like trim, tinted windows contrasting with body color, or vehicle wrap/advertising)? Always visible.

If all the cars were hi-viz colors it wouldn't make one damn difference in visibility... except that all the cars would suddenly be visible in contrast to the background. That's it. Cars would actually be less visible with each other (ie, you would be less likely to tell if a car made a sudden move) because hi-viz colors are limited and there is, again...

wait for it....

less contrast.

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Exp001

Here is my point

http://www.youtube.com/watch?v=XFLTa1_SYfs

I can't resist

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I never took drugs to improve my performance at any time. I will be willing to stick my finger into a polygraph test if anyone with big media pull wants to take issue. If you buy a signed poster now it will not be tarnished later. --Graeme Obree

A meta-analysis of randomised trials suggests that hi-viz colors increase visibility of cyclists, but none of the trials measured accident/injury rates.
http://www.ncbi.nlm.nih.gov/pubmed/17054171

An observational study from NZ suggests that cyclists who wear hi-viz have fewer crashes and days off work due to crashes, after adjustment for kms ridden.
http://www.ncbi.nlm.nih.gov/pubmed/18245309

For motorcycle drivers (not cyclists), light helmets and daytime headlights are associated with a lower risk of injury or death.
http://www.ncbi.nlm.nih.gov/pubmed/14742349

Its 1992 all over again.

+1
just that

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Wilier Cento Uno
Colnago Master X-light
Wilier 18carati

Sharing the road with cars is dangerous. A small reduction in danger is ... small. For me, not worth dressing in colors that offend my sense of what's cool (all black is cool). But I don't ride at night, and use Blackburn flea lights front and rear during the day.

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Saura mon coeur que mon cul poise.

adapted from Rabelais

Those delta brakes look cool...but weigh a ton