Last week I was bicycling on a one-way arterial-type street (16th southbound, near "the connector"). I was in the bike lane on the right side of the pavement.
As I approached an intersection, a car that had been stopped (at a stop sign) began pulling out from the left side, on an apparent collision course with me. Assuming that the driver hadn't seen me (it happens!), I used my horn substitute - I shouted "HEY!!" - and covered the brake levers, ready for evasive maneuvering.
The driver slowed down about halfway across the intersection, allowing me on through. It was a woman - and her face was contorted in an expression of barely-suppressed rage. (Think "Cruella DeVille.") Her mouth was moving 100-miles-a-minute... thank goodness I'm not a lip reader!
I don't know if Cruella was angry because of my mere presence on the road, or because I hollered, or because I was holding her up and wasting her valuable time. (Or maybe she was mad about something totally unrelated to the intersection situation... who knows?) But she and all motorists have to understand something.
If I don't know whether you intend to proceed into my path, or slow down and allow me on by, or what... I have to anticipate the worst. It's not a matter of courtesy as much as a matter of survival. I'm confident if Cruella had pulled out as another car was approaching the intersection, she would've got at least honked at!
When you start rolling out into the intersection, you waste everybody's time, besides being the cause of unneccessary anxiety on everybody's part. Be a good roadway citizen and just wait patiently until it's your turn to proceed. Thanks!