I have about 6 helmets that I've broken. I've saved them all so that anyone that visits can see the value of wearing a helmet (they used to be in the shop). I've crashed on them from just over walking pace (but going down a 15 foot drop off) to 45+ mph. I landed mostly on my head in two crashes and spent a few hours in an emergency room after one of them.

I've also fallen a few times without a helmet (this was in the era of "a hairnet is a helmet") or with a ridiculous excuse for a helmet (similar to the head fairings used in earlier Tours - plastic shell with some foam strips for fit). Once I got knocked unconscious in the middle of a road, became aware of my surroundings when I realized a lady was screaming in my ear, "Don't you think you should get up and sit on the side of the road? I almost hit you." I looked down and saw I was sitting on the double yellow line. I had been doing sprint repeats on a TT bike (I know, dumb) and looked up to see a car parked on a blind corner in the middle of the road. I couldn't brake so I just put my hand out and slammed my head into my hand. Rear window of the car had a nice 5 finger print on the rear. I lost a minute or two as when I "woke up" there were a lot of stopped cars and a cop running towards me.

I asked my mom to buy me a helmet and I promised I'd always wear a helmet if she did. She did and I did for the next 22 years, except twice.

Having said that, many riders who wear helmets are more conscientious riders. They may ride a straighter line, be more predictable. So drivers classify ("stereotype") them as being a certain type of rider, one that rides the bike predictably. This means they can pay less attention to the rider.

As an parallel example, if I'm riding along and see a runner dressed up in running gear, flouro yellow top, hat, gloves, correct side of road, and they're trucking along at a good pace, I figure that the runner knows what they're doing. I give them room as a courtesy, signal where I'm going. But if there are cars next to me, I move whatever I can, confident that the runner won't barge into me.

However, if I see what I perceive to be a "derelict person" (not sure of the correct term here) I have no idea what they're going to do. Ditto kids (not college, like 6 year olds), people with shopping bags, animals, or anything weird (guy with a shopping cart in the middle of the road, or a woman in a wheelchair in the same spot). Then I slow down because anything can happen.

So...

When I ride and traffic gets a bit close, i.e. they are not waiting just a bit to pass and are starting to take some what I consider to be unnecessary risks, I start riding a little unpredictably. I stand up, rock the bike, weave a bit too much, and generally make myself less predictable in a predictable way.

Almost immediately the drivers give me more room. It's one of those "I thought he was a good rider but I realize now that he sucks".

The study would be more revealing if you plopped a helmet on an otherwise identical person, i.e. kids or derelicts or whatever. I think a beat up helmet on a derelict would ellicit the same reaction from a driver as no helmet on a derelict. They still ride unpredictably etc etc.

cdr