It seems like every time another bike passes you and waves, you are  in the middle of a shift. This leaves you fumbling to expedite the shift  and get an arm out there, which will either lead you to stall, or else  weave around the street like a drunken toddler experimenting with mom's  high heels. Either way, by the time you've managed to get your hand up  in return, they're long gone, and completely despising you and your  rudeness. Oh yeah, and you're probably also sliding your bike through  the median. But it's the dislike that 
really smarts. 
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Notice that she's looking at literally everything but the road.
 2) If you do manage to see an oncoming bike with enough time to get  an appropriate wave up, you better make sure it isn't a scooter.  Unwritten bike rules make it a crime punishable by exile or death to  wave at a scooter. And damn if it isn't hard to tell when you two are  approaching each other at a combined 100 mph. If you do catch yourself  mid-wave to a Vespa, however, it is acceptable to slowly turn it into an  upraised middle finger. It's like the handshake-psyche of the  two-wheeled world, and the look of dejection on their face will redeem  any momentary awkwardnes