I've always worn a Helmet, now I'm even MORE convinced...
Last September my Wife had a really bad Crash, she split her Helmet in two places, it looked like someone had beat it with a Ball Pein Helmet, in fact, we've loaned it to our Friend at our LBS to show people....
So anyway, we have a Friend staying with is who came out from the UK, we loaned her one of our Spare Bikes and we all went out for a Ride today...
We were about 100 yds from our starting point, I was about 2 bike lengths behind her, taking a left hand sweep she left the paved road and dipped into a 1" drop onto the dirt, unfortunately, she tried to correct by turning back onto the paved surface and WHAM!! It was like slow motion, the side of her head hit the Tarmac first...she was out cold for a few seconds laying kinda face down...I Braked as hard as I could, dropped my bike and by the time I'd got to her she'd come around...she has a bump the size of an apple on her left cheek bone...she stood up eventually and it was like trying to hold a drunken Sailor upright...I'm sure passing Cyclists must have thought we were dancing...
Unfortunately, she also broke her wrist, we took her to the ER and it's completely smashed...she has to have surgery as soon as they can schedule it...what a Vacation huh???
But I'll never forget the way her head bounced off the Tarmac, luckily we'd loaned her a spare Giro Helmet too!!! And she wore it willingly...I know for a fact that if it wasn't for that Helmet she would have deffinately suffered some kind of head trauma...as it was, she was pretty dizzy...