Eventually we will get to cycling, but let's start with vehicles and pet peeves. It irks me no end when other drivers fail to use their turn signals. There is really no valid excuse not to, 99+% of cars on the road have them. Of course, if you have your cell phone (or your beer, or your teensy dog, or your lip stick) in your left hand and are using your right to turn the steering wheel, then it becomes cumbersome (but not impossible) to flick the turn-signal lever. I'm of the opinion that in many cases it is a power-play, a form of domination. The driver refuses to use the turn signal because everybody should just look out for him. It is the same mind-set of those who refuse to wear seat belts because "the government can't tell me what to do."
Well Luke, what we have here is a Failure to Communicate. Most of the time, nothing untoward happens. Occasionally there is an accident. Why am I harping on this now? Because I had to go to south Austin (from north of Austin) in rush hour traffic this morning. I allowed myself plenty of time so I was apparently the only one on the road not trying to gain a couple of car lengths. I lost track of the number of lane changes made without signalling their intention. Then again, if you signal your intention, the guy in the other lane might just accelerate just to close you out. Then you tempt road rage.
As for cycling: I've had drivers yell and/or make obscene gestures at me because I didn't read their mind as to what they were doing, and thus found myself inconveniencing them by making them slow down or stop to avoid me. I really appreciate not being hit, but had they just used their X&#$! turn signal, I would have gladly given them the right-of-way. My philosophy is the car is always right, my fragile bike and body have no ego in this regard. I have no desire to be dead right; my plan is to ride the next day and the next.
When by myself, and cars are visible, I always signal my intention. When riding in a group, it is always protocol to call out road hazards and slowing/stopping, cars left, right, ahead or behind, and anything else your buddy might need to know in order to stay safe, including left turn and right turn. I know, that was in a recent post.
I just shared a Google+ post about a cyclist who died in New Jersey. Facts are sketchy/unknown, but I suspect somewhere in the mix was a failure to communicate. Save a life, yell out or gesture, or if driving, use your turn signals.