I have always proposed to others that I believe that traffic on LA freeways follows a “traveling wave theory”. I believe the slow down causes a traffic “plug” or heavy concentration of vehicles. And that Jam moves down the freeway as a traveling wave. I have always wanted an opportunity to look at the traffic jam from the air so I could see if it did not actually move down the freeway. I wonder if it would obey the mathematical laws of partial differential equations when we studied traveling waves. I can still have nightmares thinking of trying to write the equations of motion for the wave traveling in a guitar string that in one case was fastened at only one end and a different case where is was not fastened at either end and when plucked how would it vibrate.