Remember kids... always wear a helmet. (The almighty bikeradar helmet thread)

Of course you can't tell they're female, because of the amount of equipment they're wearing, that is my point, you'd notice if it is a female if she's not wearing a helmet and/or let her hair down.

Even if she wasn't wearing a helmet, how exactly would you assume someone's female front of you, say for example hasn't got long hair, short cut, and isn't wearing typical girl clothes?