[nimih]

On the other hand, when I'm cycling, I'm typically not moving at >15 mph or so. When I'm walking, reduce that to 3mph. That seems like it would do a lot to counteract the car's crumple zones and airbags in terms of severity of injury.

In fact, once you take into account severity, the GP's claim seems extremely suspect: maybe the chance of any injury on a bike or by foot is higher, but I'd be skeptical of claims that the same applies to death, or even chance of serious injury (since that's what I, personally, care about), without serious backing evidence.

[jacquesm]

I knew a lot more people that died cycling than I knew people that died in car accidents. And all of the cyclists got hit by vehicles.

[nimih]

I'm in the opposite situation, personally. Irregardless, the point I meant to convey is that I'm able to talk myself into both the original claim and its converse, so it's probably better to actually point to a statistical study than try to provide a causal explanation, no matter how compelling.

[jacquesm]

I think it very much depends on where you live. Here cycling is super popular and so you can expect more deaths even if the deaths per distance number is likely quite low even when compared to places where cycling is less popular due to infrastructure differences.

[zodiac]

You can cycle at 15mph and have a car crash into you at a much higher speed

[nimih]

Yes, exactly: there would seem to be factors that both increase and decrease the risk of both activities, so the relative danger of each one is an empirical question, not something which can be deduced from first principles.