Next time you feel yourself getting impatient with rude bicyclists, consider the case of Christopher Thompson, who acted on his impatience. Yes, I know: Most cyclists follow the rules and are thoughtful to others. But just last weekend I was one of a line of cars that had to swerve around bicyclists riding three abreast on Danville Boulevard in Alamo. It was annoying - so I thought about Thompson, a 60-year-old former emergency room physician.

In Thompson's case, two cyclists were riding side by side on a narrow road near his home in Brentwood in Southern California on July 4, 2008. When he told them to ride single file, they made rude gestures, which apparently so infuriated Thompson that he pulled in front of them and braked hard. They tumbled onto the back of his Infiniti sedan, one smashing through the back window, breaking his nose and front teeth, and the other falling to the pavement and separating his shoulder.

The case inexorably wound its way through the justice system, and in November, Thompson was convicted of assault with a deadly weapon. In January, he was sentenced to five years in state prison. He wept when sentenced, in Los Angeles County Superior Court, as well he might. He said at his trial that he was only stopping his car to photograph the cyclists, but a police officer testified that at the scene Thompson had said he hit the brakes to "teach them a lesson."

The one who learned the lesson was Thompson. No matter how angry you might get at rude bicyclists - or rude drivers, or even rude pedestrians, for that matter - you have to remember that you are in a great big car that could really, really hurt somebody.

When I'm the "little guy," that is, walking, I'm only too aware of my vulnerability. It always amazes me to see people step out in front of cars, in parking lots or in the street. I don't care if I have the right of way or not. I'm an unprotected pedestrian and the others are two-ton cars or possibly fast-moving bicycles.

Which is another thing. Shouldn't bicyclists keep a more leisurely pace on Danville Boulevard? That thoroughfare has many, many side streets with many, many vehicles pulling out of them all day and night. When those drivers stop before turning onto the boulevard, they look for other cars, bikes and the occasional pedestrian. But just how visible are the bikes and the pedestrians? Any pedestrians - even runners - will be moving fairly slowly and will able to avoid the car hitting them. But those bikes that go 40 mph are an accident waiting to happen. Aren't they afraid of the cars pulling out from the side streets?

Spring is right around the corner (I hope, I hope), time for the cyclists to enjoy our country roads to an even greater extent than they have been during the last few months. Except they are not quite country roads now, are they? despite the beautiful trees that line most of Danville Boulevard. Surely there are roads in the vicinity where one can zoom along at high speeds to one's heart's content without any danger. But Danville Boulevard is not such a road. Neither is the Iron Horse Trail, except for certain times and places.

So while this is a plea for bicyclists to please be polite as they enjoy getting exercise on streets that were designed for cars, it is also a cautionary tale for the drivers of the cars: Control your road rage; your car is a deadly weapon. Remember Dr. Thompson.