The black BMW had a problem. It had an aggressive posture, that sense of agitation that a car exudes when its driver is raging behind glass at all the other jerks on the road, or maybe raging about some private distress, but in any case raging. It was midafternoon on River Road and not yet crowded; it seemed a little early for bad tempers.

Pretty quickly I got the sense that it wasn’t all the other jerks on the road who had drawn the ire of the BMW driver but your humble correspondent in her deeply unfashionable minivan. With traffic moving at a relatively swift 45 mph, I felt as much as saw the car pull close to my back bumper. Then it darted into the right lane and began to pull even with our vehicle, very close indeed.