Saturday, April 19, 2008

Conspicuity and Crashes

A study of bicycle crashes here:

and one of motorcycle crashes here:

both show that riders who wear high visibility clothing have much lower crash rates than their more subtly-dressed peers. One problem with such studies is that human beings are complicated creatures. For example, the cycling study states:
Risk-taking behavior is a potential confounder in all observational studies of injury and is difficult to measure reliably because of the likelihood that participants will provide socially desirable responses. "Reverse causation" can also complicate cross-sectional analyses, if outcomes influence exposures. In this study, such a mechanism would be expected to reduce associations rather than inflate them—for example, a bicycle crash may prompt a participant to use fluorescent clothing.
In other words, if you're prone to be a risky rider you probably won't identify yourself as such and if you've had an accident you might load up on safety gear. And I personally think one huge confounder might be this: folks who think a lot about safe riding will probably be far more prone to be swayed by safety considerations in the purchase the fluorescent gear. Riders may not be safer because they are wearing the bright colors, they may be wearing bright colors because they are more safety conscious riders.

While it is very hard to allow for all the confounding factors, both studies suggest that brightly dressed riders have lower crash rates. In any case, I figure my habbit of wearing a bright yellow vest while riding can't hurt.


Marrock said...

Speaking for myself, I've no problem with wearing a helmet but there's no way in any of the nine hells I'll ever be caught running around in day-glo clothing.

As a matter of fact, the helmet would be the only specialized article I'd wear for riding.

And for the record, I've never struck or been struck by a car or pedestrian.

I also follow the rules of the road, stop for lights and stop signs, avoid the sidewalks like the plague, and have no problems taking the lane when required.

Emily said...

I've noticed that multicolor outfits can be hard to see. The colors and patterns seem to blend in with all the other colors and patterns in a city.

A solid color seems to give more visual weight. I have an easier time seeing other cyclists when they wear a relatively bright solid color. Powder pink, fuschia, red, yellow, and orange all seem to work fairly well in a temperate climate. Yellow is not as good as I'd like against snowbanks. White is good in summer, but awful in winter. Bright greens are good in winter, but are problematic in summer. It's surprising how well fluorescent green blends in with the trees in the Arboretum *g*. Blue can work well in hilly areas since then you're contrasting with green and brown.

It's pretty easy to find jackets and shirts in a color I like *and* that is easy to see. Fluorescent clothing isn't required to get good contrast.

Anonymous said...

I wear a 'safety yellow' coolmax t-shirt, red or blue tights and black shorts whenever I'm on the bike (a recumbent). Yes I do look like I escaped from the clown troupe at the circus. But if people are laughing and pointing at me, that means they SEE me and are far less likely to hit me.
- Rick

nollij said...

Speaking for myself... I wear a safety orange helmet (the Bell Citi), Hi Viz Yellow & Safety orange vest with Reflective stripes (picked up in London, made by Respro), Glo-Gloves over whatever other gloves I'm wearing. I generally wear black or dark clothing (I don't like to wear colors generally) so I do this to increase my conspicuity. I've only been involved in 1 car/bicycle crash and it was back in high school. I was IN the crosswalk and it was a hit and run... I chased the driver, but I was too shaken (and unaware of the value of it) to get the license plate number.

I also ride a motorcyle and I wear a hi-viz aerostitch roadcrafter suit and a orange and white helmet, but I definitely take more risks when I ride a moto than when I ride my bicycle. Either way, I feel like I'm evening out the odds against me by a smidgen. People laugh sometimes, but they're generally not the ones who ride bicycles for transportation.

Anonymous said...

It's really hard to use the motorcycle data, because the demographics are so different. You have young sportbike riders, who (as a rule) ride too fast, and older "born again" bikers who tend to ride cruisers, not very well. Those are the big groups for fatalities, and neither would be caught dead in high-viz gear.

But I think that image is bigger deal for motorcyclists than cyclists, though perhaps not by much.

Note that I'm being general here. I taught MSF ERC classes for a decade, and saw lots of young sportbike riders and older cruiser riders who were skilled and careful.