I have a lot of doubts about this.

Is this adjusted for location? I imagine people may bike on sidewalks more in dangerous-for-cyclist cities.

According to the CDC, most (72%)[1] of bicycle deaths occur outside of intersections, so this may even be an acceptable risk. Most fatal crashes occur near, but not in intersections[2] - biking on the sidewalk completely avoids them.

Also, when you're biking on the sidewalk, your odds of getting doored into traffic go down substantially.

[1] https://www.cdc.gov/motorvehiclesafety/bicycle/index.html [2] http://www.nyc.gov/html/dot/downloads/pdf/bicyclefatalities....

If you had biked in both places, you wouldn't doubt it. Sure not every autocager sees (or drives as if they see) a cyclist in the road, but the cyclist can see and hear everything around in way that's just not possible on the sidewalk. (I say this as someone who is missing one eye.) Also, cars aren't the only things with doors.

I have biked on both places (In more suburban areas). The roads tend to be terrifying (Because try as I might, I can't keep up with 30 mph traffic.) The sidewalks tend to be empty. I also didn't blow through intersections, which minimized the risk of getting hit in one.

Cars aren't the only thing with doors, but they are the only thing that will door you into traffic. Doors flush with buildings are also quite rare, and are quite rarely opened. (Except store doors - but you don't want to bike near them anyways, unless you want to run into a sign, or a table, or an outdoor display.)

I feel like I'm missing something. I can't understand how it's more likely for a car to hit a cyclist on the sidewalk than the road. Cars drive in the road. They do not drive on the sidewalk.

I hit a car while riding on the sidewalk as it was exiting an alley. The problem is that when you are riding on the sidewalk in a city, the corners are too blind. In order to guarantee avoiding an accident you essentially need to stop at each driveway and alley. Most cyclists and drivers aren’t going to do that. On the road you are far enough back that you can see cars exiting; they can see you as well.

They drive across the sidewalk when entering or leaving driveways, and drivers do not always see cyclists in those circumstances.

Unless they make the same people bike in a randomly decided way during the study, it's likely selection bias to a large extent - more experienced cyclists would ride on roads, less experienced (and on worse bikes without disc brakes) - on sidewalks.