Get me to the church on time… |

So, for the past two years, I have not driven a car. Which means I rely on others to get me where I need to go. (It also means I have missed a boatload of Phillies games. Sniff, sniff.)

And, while I am in the passenger seat (a heretofore most unusual position for me), I have noticed that the drivers today are simply crazy- and I am being extremely charitable. They think nothing of making a right hand turn in front of us- from the left hand lane. Or, zip around the breakdown lane to pass us.

Given this meshugaas (Yiddish/Hebrew for insanity), I am not surprised that traffic conditions have been terrible. Despite the fact that the number of cars on the road are still down compared to pre-pandemic conditions.

And, it’s the craziness of drivers that seems to cause traffic to bunch up. That guy who just passed us on the right (in the breakdown lane), cuts back in and causes my driver to hit the brakes. Which then causes five or six cars behind us to hit the brakes. Propagating a slowdown that can extend to a mile, if there are enough cars on the road.

This is the sort of phenomenon that traffic/transportation engineers have been examining for a while. They have noticed that equidistant vehicles, generally moving at the same rate of speed, tend not to stay in that configuration for long. One driver darts in or out and that perturbation effects what they call a ‘phantom traffic jam’. (It’s termed as such since the traffic is free flowing, with no obvious reason for the blockage to have been caused.)

These perturbations have become known as “jamitons”. They are similar in concept to “detonation waves”- when a shock (a sharp jump in vehicle density) occurs in one location- while there’s a smooth decay on the other side. These waves as stable enough to be maintained for a long distance. (The word jamiton is borrowed from the phenomenon of traveling waves in other fields, which are known as solitons.)

This is exactly what five researchers (Rodolfo Rosales/MIT; Morris Flynn/Alberta; Aslan Kasimov/King Abdullah U of Saudi Arabia; Jean-Christophe Nave/McGill, and Benjamin Seybold/Temple) have been studying via NSF [National Science Foundation] grants (DMS-1007899 and DMS-1007967), Phantom traffic jams, continuum modeling, and connections with detonation wave theory.

It’s why these folks recommend use of variable speed limits. By slowing traffic gradually, they can prevent the perturbations that occur when a single car slows abruptly. (They also claim this not only maintains the flow of traffic, but reduces crashes by about 1/5.) Moreover, controlling traffic via variable speed limits (using LED speed limit signs) is much cheaper than requiring an additional lane of traffic, to accommodate the frequent traffic jams.

Which brings up another situation. Dr. Alex Bayen (UC Berkeley) noticing the same phenomenon, recognized that consistent speed and distance helps maintain traffic conditions. So, as more automatically controlled vehicles take to the road, traffic will become “smoother”. And, it will also improve fuel efficiency. Now, the trick is to develop the AI (artificial intelligence) and coordinating systems to let these traveling cars communicate with one another, to maintain traffic flow.