If I'm going to the drug store, and choosing between car and bike, which would be safer? I have to look at it per mile.

If I'm driving for pleasure, just to look around, or riding for fun, I think of it as a block of time and I'd look at it per hour.

If my driving destination is one that I'd never bike to, I don't see the point of comparing them.


Yeh, that's my main objection. I'm not real wild about Walker's methodology either.

No, you don't "have to" look at it that way.

If the drug store was 20 miles away, you would drive. If it was next door, you'd walk.

People usually have a "set" amount of time do do things "for pleasure". If they have a 1 hour "block of time", then they can ride for 12 miles or drive for 50 (it's very unlikely that they would drive at 12 mph for an hour!) Thus, the risk is more related to time than it is to distance.

At issue is comparing the risk of cycling versus driving. A related issue is people choosing to drive when they could ride instead. The overal risk to a population isn't related to the your choice.

Walker stressed that it was one study in one place and that one might not be able to expect that the results were universal.

It points to the problem of studies with the anti-helmeteers too: studies that don't support their position are fatally flawed and studies that do are perfect.

But no one is interested in an effect that lasts "a few minutes".

I suspect they would have ridden more slowly if they were required to ride naked.

"The findings are consistent with the notion that those who use helmets routinely perceive reduced risk when wearing a helmet, and compensate by cycling faster."

That's not the only "notion" that the findings could be consistent with. It's possible that they'd start riding faster over time even without a helmet.

They probably see riding faster as a "percieved increased risk" inherently and compensate by wearing helmets (that is, the choose to ride faster and helmets are available).

For cyclists not accustomed to helmets, there were no changes in speed, perceived risk, or any other measures when cycling with versus without a helmet.
These riders ride slow and still ride slow with a helmet. One reason the Dutch injury rate is low is because they mostly ride at around walking speed. The anti-helmeteers want just want people to ride slow!

Yet that's what the study bases its conclusion on. At the least, they didn't check against that likely possibility.

There is a logic fail in the conclusion as well. Reduced speed (or greater risk) when taking the helmet off is not synonymous with faster speeds or less risk when putting one on, but that's how they conclude. At least they qualify it with "those who use helmets routinely", yet a mandatory helmet law would be pointless for those who routinely wear helmets while for those who do not (the point of a MHL), no difference in speeds (risk) was observed.

We are comparing the risk of driving vs cycling to this drug store. That risk when cycling is 3-5 times the risk when driving. Do you disagree?

Saying that "cycling is no more dangerous the driving" is incorrect when either trip is to a particular destination.





That what I said, for the case of recreation.

You may think this is splitting hairs, but risk to a population is not the same as the risk of an activity, and I think that you're making a mistake in conflating the two. You are adding variables: car-free cyclists will take fewer trips for example, perhaps shorter ones. Most people aren't going to find it credible to say, for example, cycling is safer because you biked 1.5 miles to Taco Bell instead of driving 15 miles to Burger King.

For the activity, hold other things equal. Same purpose for the respective trips, same destination, what is the risk.

Yes. That's my problem with that study.

I don't know. Nor do you. From my estlmates based on the number of deaths, it seems to me that the risk of dying per hour is about the same for driving and riding. I suspect that people spend about the same amount of time transporting themselves whatever mode they use (and travel fewer miles when riding than driving).

I suspect it's true generally (not just for recreation). People likely tolerate 1-2 hours of regular/daily transportation. If they drive 1-2 hours a day, there's very little chance that they'd choose to ride instead.

All risk assessment is based on a risk per population. The risk to a specific individual is likely quite different than the overall risk to an "average" person with in a population (the risk is going to be different, too, for different subpopulations).

Of course, they will take shorter trips.

I suspect that people spend around the same amount of time in transit regardless of the mode. People who cycle ride fewer miles and people who drive drive many more miles.

If you compare risk-per-mile, it biases against cycling because it takes a huge amout of time to match driving miles.

Mostly because risk-per-mile doesn't make sense.

The 1.5 mile trip by bike is about the same amount of time as the 15 mile trip by far. As far as I can tell, the risk per hour is about the same. Since you wouldn't really ride the 15 miles, the only way to compare the risks is per hour.

Getting a precise number for accidents per mile is difficult because we don't know precisely how many miles are actually traveled by bicycle. But I do know this much: estimates top out at 21 billion miles for cycling in the US per year. 726 deaths /21 Billion miles = 34. Data is good for auto passenger fatalities.

34 fatalities per billion miles traveled, bicycle
11.4 fatalities per billion miles traveled, passenger vehicle.

At the very least, since 21 billion miles is the very highest estimate for cycling, cycling a given distance three times more dangerous than driving.


I know where you're coming from, half of US trips are short, 5 miles or less, and very short rides take about the same time as driving. But still, you're comparing the cyclist who seldom or never drives to the driver who doesn't bike. That IS one way to compare risks. But I think that most people, me included, want to know the risk of riding to the post office vs driving there. I have a car in the driveway ready to go, bike in the hallway, and I'm going to Kroger. How much riskier, if any, to take the bike? I'm not saying that it's a significant risk either way, but to be honest it's at least three times the risk to cycle, more if we consider all injuries (and not just fatalities).

Your estimates are neglecting consideration that not all miles are the same in risk to the driver and rider. Cars can be driven on just about any street or road without much driver concern/anxiety about increased personal risk from the specific traffic density or velocity, or the width of the road, or the presence of road shoulders. For the cyclist, those riskier traffic scenarios may rule out riding the riskier miles even if the distance and perhaps even time is identical to driving those miles. The traffic stats you cite presumably reflect cyclists' collective decisions to avoid cycling at all on the cycling unfriendly miles, even for relatively short distances.

This is the assertion of the study I posted -- those who wear helmets experienced higher risk and rode slower without helmets, meaning they ride faster and "riskier/less safe" when they do wear helmets. Bareheaders, however, did not ride riskier when they wore helmets.

So it appears that this study confirms that helmeteers ride less safe than do bareheaders...

No, that doesn't follow, neither of the bolded fragments.

First, the people putting on helmets did not experience higher risk. They did not ride slower. They did not "perceive" any difference in risk levels. The study acknowledged this explicitly.

Second, the people who "routinely wore helmets" also did not experience higher risk when wearing a helmet. They "perceived" a higher risk when taking it off, which does not mean that there was an actual higher risk experienced. Just a feeling. They did pedal down the 1/4 mile hill more slowly, immediately after taking the helmet off. If anything, it confirms that "feeling" of higher risk but nothing more could be concluded. It does not follow that they would ride faster when they put the helmet back on, other than on the immediate 1/4 mile hill.

The problem with this is that most people spend much more time driving than they do cycling. "three times more dangerous than driving" sounds bad but it does't reflect how people really cycle or ride.

Distance, as I said earlier, is an unfair way to compare cycling risks.

Because people tend to drive for more distance than they would cycling.

Assuming a 12 mph speed cycling and a 46 mph speed driving, then the risk per hour is the same.

That is, in practice (the real world), the higher average speeds when driving make up for the lower risk per mile. Because, on average, people in the real world tend to drive many more miles than they cycle.

It isn't perfect, but it's more fair to compare the risk-per-hour.

I'm not making that comparison at all (it's not possible to do anyway).

That's not "honest" at all.

On average, in the US, people drive 12,000 miles per year and ride a few hundred miles.

And the "three times" risk might not apply to you particularly at all (meaning the real/actual risk to you isn't "three times").

Clearly, if you never drive, you'd be safer driving!

You still really don't know. Keep in mind that your actions can drastically increase or decrease your personal risk relative to the average/aggregate risks we are talking about.

I would not dispute that biking on those roads that cyclists mostly avoid would result in higher risk factors.

So, considering all roads and not just those preferred by cyclists, the risk would likely be even greater than the 3-5 times higher than driving which I've cited.

Agreed; and on some of those usually avoided by cyclist roads/streets to desirable locations (i.e. high speed narrow roads with heavy traffic, late night travel to night spots on streets frequented by thuggish layabouts, etc.) the risk to those few (if any) cyclists would likely be even much higher than if the cyclist had decided to travel in an enclosed motor vehicle.

When I switched to off-road riding exclusively I started wearing a helmet full-time, because I suck at off-road riding. I've been doing it for a few months now so don't suck quite as much, and started leaving the helmet at home on occasion. I've noticed that I fall off less without it. When I'm wearing it I "take my chances" even though I don't consciously feel safer with it on. When I'm not wearing it I get off and walk the "riskier" sections. I'm pretty sure that's the whole concept behind the "risk compensation" deal. I honestly don't know if my head is any safer with or without the helmet, but the rest of me definitely stays in better shape when I go bare-headed.

So much for the helmeteer argument that it's not speed but rather distance to the ground.

Hell, the entire debate ignores the fact that there are different kinds of bicycling. It would be very convenient if we could quantify some general "danger of cycling" figure, but it should be obvious that the downhill mountain bike racer and the ex-pro doddling around on the bike path and the Copenhagener on his way to work have essentially nothing in common but two wheels.

Tell it to all the folks on this forum who have posted something along the lines of "and when I realized I'd forgotten my helmet I turned around and very carefully rode back to my car to get it." I mean, it is courage for your head, after all.

I started cycling seriously in 1974 no helmet and rode like an @zz. I started wearing a helmet full time in 1988 and rode like an @zz. It's 2015, still wearing a helmet and still riding like an @zz.

I don't think about my helmet when I am cycling. I think about what I am doing - what is going on around me. What color socks I am wearing or what kind of hat is on my head is about the farthest thing from my mind in the trenches.

It would be interesting to hear about how you rode if you took your helmet off now. If you are like most of today's cyclists I suspect you would feel surprisingly vulnerable without it, especially after having become so accustomed to it.

I ride without a helmet the same speed I drive without a seatbelt.

Unsurprising how some studies get confirmed here by anecdotes.
But some other studies? Garbage, I tell you, garbage! Utter rubbish! Magic hats!

Another (significantly more reliable) way to find out the quality of a study? Look at the cites of the study. (I know, I know, using scholar.google.com is so hard.)
Most of the papers cited by the anti-helmet crowd don't stand up very well. (I'm understating the science here.)

This paper is a survey of SOME of the MANY follow up studies published on many of the studies commonly cited here.

For example, Walker, I (Drivers overtaking bicyclists) does not hold up well at all. As in, not at all.
(Apropos nothing at all, some of the same people who object to a "small sample size" of 1,000 glowingly cite a study with a sample size of ONE.)

The "risk compensation" papers now being discussed here don't hold up very well either.

-mr. bill

I did some rock climbing in my younger days. Always free climbed until I took a class. They sure ruined my confidence with all that safety gear...

That would be undiplomatic. But I have several times suggested riding without a helmet every once in awhile, for this same reason. So that we don't become psychologically dependent on it. Generally, if I've been wearing a helmet consistently, I'll feel vulnerable for five or ten minutes and when that feeling passes I'm riding exactly as normal.

We're discussing driving risk vs cycling risk in the last few posts, so it's only about the kind of bicycling that corresponds to a trip taken in a passenger car. At least I am - njkayaker broadens the scope to all varieties of driving vs the total amount of bicycle miles so you have a point regarding that side of it.

I would say that their lower speeds make accidents less likely (along with their infrastructure, shorter commutes, milder weather and different traffic patterns but that's another debate). The "helmeteer argument" is that the impact with the horizontal ground is independent of bicycle speed, or car speed. Two different factors.

How many "helmeteers" have actually argued that speed has nothing to do with the severity of injuries?

Bizarre. Your 3 times more dangerous" statistics treats all riding and all driving as the same. You are doing the exact "broadening" you are complaning about. What you are doing is worse because you think that statistic is an "honest" measure of the actual risk an individual is exposed to. Actually, that risk is a (very rough) average and the risk to individuals likely has a very wide variation. Bizarre.

I believe the accidents-per-mile is different between for highway driving (lower) and other roads. If so, that would mean your "honest" three-fold increased risk is too high because you are "broadening" to include "all varieties of driving".

Anyway, no one (including you) can get statistics without any "broadening".

You made that argument (without being a "helmeteer").

First, I did not fail to notice the issue pointed out by the bareheaders who donned helmets for the experiment. In that sense, it did nothing to prove risk compensation.

But second, the language of the study indicated that the helmeteers ride safer/less riskier/slower when riding with no helmet. No getting around it -- they ride riskier/less safe/faster while wearing a helmet than without. The subtext is that those who routinely ride with a helmet also routinely ride risker/less safe/faster than they would otherwise, confirming risk compensation is in effect for those wearing helmets.

I agree with you on the first point, but not the second. And if anything, I believe the whole study points out how weak the risk compensation issue is regarding this Great Helmet Debate -- so weak that it should not even be considered when discussing bicycle helmets.

However, the original contention was that there were no risk compensation studies, and... there are...

Any credible source for these alleged factoids?