Two recent road rage incidents are all over the news in Portland. Earlier this month, a drunken man on a bike became aggravated when a driver, himself a self-described bike advocate, reprimanded the cyclist for blowing a stoplight. The cyclist threatened the driver, picking up his bike and hitting the car with it. Then this week, a driver struck a cyclist and continued to drive as the victim, who escaped without serious injury, clung to the windshield.

The aggression on display is hard to fathom, but does it merit front page coverage? The breathless headlines pitting cyclists against drivers have led BikePortland’s Jonathan Maus to critique the local press for exacerbating the us-versus-them mentality.

There’s no excusing dangerous behavior on the road, no matter how you choose to get around, but the level of violence people are capable of when they’re driving is, by the nature of the vehicle, quite considerable. As one commenter on the Oregonian’s web site put it, "A drunk cyclist is clearly a menace, but a drunk driver can be downright deadly."

And then there’s this story (via Tom Vanderbilt) out of Seattle last Wednesday, when a man was killed for setting up orange cones while he gardened in a traffic circle near his house, showing that people don’t always have to be behind a wheel for their entitlement to the road to turn fatal.

Here’s a question for Vanderbilt, whose new book, Traffic: Why We Drive the Way We Do (And What It Says About Us), will be released later this month. What is it about automobiles or the road or human psychology that makes people behave like sociopaths at times?