I crashed on my bike Oct. 3 and broke my collarbone, an experience so horrific that my first impulse was to say I would never ride on the road again. Turns out I am not alone. 'Well, you've joined the proud majority of serious cyclists who've busted a collarbone,' said Rob Coppolillo, a competitive cyclist in Boulder, Colo., who also leads rock- and ice-climbing expeditions and is a part-time ski guide. I've since heard from other cyclists who broke bones or were badly bruised and shaken up in crashes. Many say they, too, vowed, at least initially, never to ride outside again. It's not a universal response, but it is so common that cyclists nod their heads when they hear my reaction to my injury. Yet almost no one swears off running after an injury, even though -- and I speak from experience -- a running injury can keep you away from your sport at least as long. And that made me wonder: Is a cycling injury qualitatively different from a running injury? Is it the drama of a crash, or is it that a crash makes you realize you could be killed on a bike? Is it the type of injury? Or the fact that you can feel, as I did, that the accident was unfair and out of your control? Risk-assessment experts say that it is all of the above and that the way we respond to various sports injuries reveals a lot about how we assess risks. My crash came 8.9 miles into a 100-mile ride (of course I knew the distance because, of course, I was watching my bicycle computer). My friend Jen Davis was taking a turn leading; My husband, Bill, was drafting -- riding close behind her. I was drafting Bill when a slower rider meandered into his path. Bill swerved and I hit his wheel. Down I went. The first thing I did when I hit the ground was turn off my stopwatch -- I did not want accident time to count toward our riding time. Then I sat on a curb, dazed. My head had hit the road, but my helmet saved me. My left thigh was so bruised it was hard to walk. Worst of all was a searing pain in my left shoulder. I could hardly move my arm. But since it hurt whether I rode or not, I decided, like an idiot, to finish the ride. The next day I went to a doctor and learned, to my shock, that my collarbone was broken. Running is my sport, I thought, and no ride is worth this. I remembered what Michael Berry, an exercise physiologist at Wake Forest University, once told me. With cycling, he said, it's not if you crash, it's when. He should know. He's a competitive cyclist whose first serious injury -- a broken hip -- happened when he crashed taking a sharp turn riding down a mountain road. Then, last June, he was warming up for a race when he hit a squirrel, crashed into a telephone pole and broke his arm so badly he needed surgery. His reaction to each crash was a variant of mine. He'd taken up cycling about five years ago because he'd injured his hamstring running. 'With each wreck I thought, 'Maybe I should try running again,'' he said. My running friend Claire Brown, a triathlete, crashed a few years ago when she was riding fast on wet roads, getting in one last training ride before a race. Her bike slid on a metal plate in a bridge and she went down, hitting her head and her left hip. She was badly bruised, and even though she broke no bones, she did not feel comfortable riding for the next two years. Even now, she told me, 'there are bridges around here I won't ride on, and I definitely won't go downhill fast.' And yet, and yet. Despite how much it hurt, my collarbone fracture was nowhere near as bad as some running injuries. When I got a stress fracture -- a hairline break -- in a small bone in my foot, I was on crutches for eight weeks. When I finally could run again, my foot hurt because the muscles had atrophied. Running was slow and difficult. I'd lost the rhythm and the stride that make running fun. With the collarbone fracture, I wore a sling for three weeks but could take it off and ride my bike on my trainer -- a device that turns a road bike into a stationary one -- and use an elliptical cross-trainer. After four weeks I could run, and running felt good. George Loewenstein, a professor of economics and psychology at Carnegie Mellon University, says there are several factors that separate running injuries from cycling ones. Running injuries are often hidden -- like a torn hamstring -- and tend to heal gradually on their own. Bicycling injuries, he told me, 'tend to be more acute and dramatic -- often there is blood or even bones sticking out,' and 'if it's a gory image, it tends to deter us.' Then there's the issue of control. 'Control makes a big difference in whether we take risks,' Loewenstein said. 'With biking, you feel in control until you have an accident. Then all of a sudden you realize you are not in control. That can have a dramatic effect -- you can shift abruptly from excessive daring to exaggerated caution.' With running, even though I realize that I and others who got injured could not have prevented our injuries, somehow I blamed myself. It was 'overuse,' even though overuse is apparent only in retrospect, as you cast about for a reason why you got injured. But running is considered to carry less risk than cycling. And, notes Barry Glassner, president of Lewis & Clark College in Portland, Ore., and an expert on fear and risk perception, 'anything that is widely perceived as lower risk, we blame ourselves when something goes wrong.' 'It's known as the world hypothesis,' he said, 'this notion that the world should be fair.' Glassner said 'we get especially outraged' when the world is not fair, as with a cycling crash. Or, he noted, 'we blame ourselves' for the injustice of it all, as with a running injury. The hypothesis does let some people continue a risky sport -- by deciding that a serious accident was not really random. 'You see it with rock climbers,' says Coppolillo. 'There will be a fatality or someone will really get hurt. There are those psychological backflips you can make yourself do. 'It won't happen to me.'' And if you have an accident and you can blame yourself for it, then you can also convince yourself that it won't happen again. That's how Loewenstein reasoned when he crashed his bike last winter after riding over a patch of ice. He ended up with a shoulder injury. He decided the whole thing was his fault and could have been avoided. 'I did not experience a loss of control,' he said. 'I just thought I had been stupid. Whereas if a car had hit me, it would have been different.' If that had happened, he said, he might have vowed never to ride again. 