My Friend (?) in the Red Ford Focus

When I travel northbound on Route 13 shortly before eight in the morning on weekdays, a man that I don't know waves at me. It is not a very enthusiastic wave. It is a nonchalant lifting of the index finger off of the steering wheel. It is barely a wave, really. More of an acknowledgment. This has been going on for months. I don't have any idea who he is or who he may think that I may be. I drive a pewter Buick Lasabre. The cadillac of middle class grandmothers. I am sure that he thinks he knows me; but he doesn't. For a long while, I would not see the wave until he was so close that I couldn't wave back. I would be on the phone with my sister, or drinking a cup of coffee, or eating a hard-boiled egg and even if I saw him wave in time, I did not have a free hand with which to respond. This catches me off guard, and makes me shake my head in wonder. Who is this middle-aged, scruffy man in a ball cap? Why does he wave? Does he wave at all the cars that pass in the opposite direction, perhaps to see if someone will wave in return? Or does he just wave at middle-aged white women? Or just women in Buick Lasabres? Or did I once give him a hard look because my 20 year old daughter also drives a red Ford Focus? Is it just a game of Sweet or Sour that he plays to keep himself awake at the wheel? Now, it has been about a year...and if I see him in time...I will acknowledge him back. Funny, there is no way I would recognize him in any other context.