I've come straight to this section of the forum, and almost didn't bother posting as I accept this is much of a muchness but genuinely found what I'm about to say 'intriguing' so thought I'd put it out there. So I've recently started running in to work, after moving home and thinking 3.5 miles isn't far enough to cycle. I'm currently running one day, then cycling the next. When I cycle I average about 17mph, and cycle fully on the road. When I run I average 8mph (if I've done the maths right to convert 7.30 minute miles) and run entirely on the pavement. I feel much, much more vulnerable running. Every time I come to a side road, I shoulder check, I check the rest of the road, but always feel more at risk when crossing those roads (about ten of them) than I ever do on the bike on the same commute in. I wear a helmet when I cycle, I don't when I run - even since acknowledging that my perception is of a higher risk when running. Mind you of course - who wears a helmet to run... So the question isn't for me "Why don't I wear one when jogging" but instead "Why don't I stop when cycling". This is the closest I've come to not bothering with a helmet since I've started cycling... (the wife wouldn't approve though).