I was driving along in the right lane of a Mountain View street the other week when I passed a motorcycle in the left lane. I noticed the motorcycle because it was being remarkably quiet (I thought for a moment that perhaps it was electric, though it later turned out not to be), and because it had slowed down quite a bit, presumably due to the driver seeing the red traffic light at the next intersection, half a suburban block ahead.
I passed the motorcycle uneventfully, at around the speed limit, and continued on toward the red light. But in my mirror, I saw what happened next:
There was a big Dodge Ram pickup truck in the left lane behind the motorcycle. The truck driver apparently got impatient over the motorcycle's slow speed. So the truck swerved into the right lane (well behind me; I was never in any danger here), zoomed past the motorcycle, and veered back into the left lane in front of the motorcycle...
...And then the truck had to come to an abrupt stop, because, well, there was a red light in front of it.
So the truck driver engaged in a sequence of unsafe too-fast maneuvers in order to arrive at the red light approximately two seconds before they would otherwise have arrived. And then they sat at the red light with the rest of us for another ten or twenty seconds before the light changed.
I imagine that the truck driver was in a hurry, and was frustrated at someone going slowly in front of them. But everyone involved would have been better off if the truck driver had managed to curb their impatience long enough to notice the red light ahead, and to give a few seconds' thought to whether unsafely passing the motorcycle was going to help them in any way.