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Explanation for Holiday Traffic Jams

I can’t tell you how many times Jerry and I been driving on the tangle of southern California freeways, when of a sudden the traffic slowed to a creep, then finally was at a stall.

“Probably an accident or something,” often I have said.

“Most likely,” Jerry has agreed.

We stalled, crept, sighed with frustration, stopped, started, then at last our speed picked up, the traffic cleared before us and we were now moving at normal freeway speed. We’ve turned our heads in all directions looking for the wreck or the road construction or the detour signs, but in vain. There seemed to be no reason for the stalled traffic. Happened to you? Doubtless, if you live in an urban area. We’ve all puzzled over the phenomenon of a traffic jam to which there is no discernable cause.

Christmas lights and traffic. Tennessee, USA

QT Luong picture used under his “private” guidelines.
Now, a team of mathematicians from the Universities of Exeter, Bristol and Budapest, have found the answer and published their findings in leading academic journal Proceedings of the Royal Society.

Mathematicians from the University of Exeter have solved the mystery of traffic jams by developing a model to show how major delays occur on our roads, with no apparent cause. Many traffic jams leave drivers baffled as they finally reach the end of a tail-back to find no visible cause for their delay.

The team developed a mathematical model to show the impact of unexpected events such as a lorry pulling out of its lane on a dual carriageway. Their model revealed that slowing down below a critical speed when reacting to such an event, a driver would force the car behind to slow down further and the next car back to reduce its speed further still.

The result of this is that several miles back, cars would finally grind to a halt, with drivers oblivious to the reason for their delay. The model predicts that this is a very typical scenario on a busy highway (above 15 vehicles per km). The jam moves backwards through the traffic creating a so-called ‘backward travelling wave’, which drivers may encounter many miles upstream, several minutes after it was triggered.

Dr Gábor Orosz of the University of Exeter said: “As many of us prepare to travel long distances to see family and friends over Christmas, we’re likely to experience the frustration of getting stuck in a traffic jam that seems to have no cause. Our model shows that overreaction of a single driver can have enormous impact on the rest of the traffic, leading to massive delays.”

So, as my early Christmas gift to my readers, I bring this explanation as to why you are now stalled in traffic in Los Angeles, Boston, New York City, San Francisco, San Diego, Chicago or Milwaukee. Relax, tune your radio away from the traffic alert station to one that is playing Deck the Halls with Boughs of Holly, or Grandma Got Run Over by a Reindeer, or best of all, Joy to the World…The Lord is Come!


My devotional blog is here.

By Shirley Buxton

Still full of life and ready to be on the move, Shirley at 83 years old feels blessed to have lots of energy and to be full of optimism. She was married to Jerry for 63 years, and grieves yet at his death in August of 2019. They have 4 children, 13 grandchildren and 11 great-grandchildren...all beautiful and highly intelligent--of course. :)

10 replies on “Explanation for Holiday Traffic Jams”

I must say I’m amazed at the variety of items that show up on your blog Sis. Buxton. In addition to, always being entertained and informed by it. This site is a fountain of information.

I’ll be close to you next week. Have a Merry Christmas and the Best and most Blessed New Year Ever. Much Love to y’all.



Yeah maybe if the highway is a true parking and nothing has moved, in a case where you actually shut down your engine because you’re just wasting gas, then possibly you could use a laptop… But in any other case (where you need to move inches every minute or so), then it would be really dangerous to do so, both for having other drivers mad at you (you don’t go forward for a few minutes and someone else moves to your lane, thus people back of you are going “WTF?”) and for you risking the state of your car (seeing from the corner of your eye that the car in front of you moved, follow, and when the car stops not notice and run into it). Granted, those are minor consequences, but still… I try to find other things to do.

Traffic isn’t nearly as bad in Montreal as it is in New York or other larger US cities, but we have our slowdowns too. This will happen a lot if either one highway exit is very slow (that slowdown will spill over to other lanes, mostly because people try to go to the front of the waiting line and cut someone off ) or if there is a burst of traffic from an on-ramp that isn’t going very fast, thus again slowing down other lanes because of people switching lanes to accelerate and ignoring the oncoming, faster, traffic.

The worst spot for us in Montreal is on a section of highway 40 (going east-west) where another highway (going north-south) merges onto the 40 for a few miles. The on-ramp from the 15 to the 40 is two lanes and merges on the 40 from the right, and the exit towards the other part of the 15 is on the left, thus every single car that continues on the 15 will need to cross 3 lanes of traffic, an exit that is only one lane – go figure. This happens in 2 or 3 kilometers, so it’s hell when there’s any traffic. That section of the 40 is basically always full of cars, because it’s two highways in one.

I’m sure there are similar situations in other cities, but it’s one example that engineering can be a major determining factor in traffic – more than the human element.



When I read this, I immediately thought of Mulholland Drive. Every time we travel south, the traffic will always slow around the area of Mulholland (I think it is on 405). There is never any reason for this jam, but it always happens.



Both may not be legal for us “in traffic,” but if there is no movement then who or how would they stop me? The Type “A” person would have the uncontrollable, need or urge to be doing something as they sit. I, personal option, would rather see them working or commutating than sitting dead still not being abler to do anything but burning because of all the time being lost. This could be because of the part of a type “A” personality that I have. As well as have sat in some of the worlds largest parking lots, like I-405 in the L.A. area.

I would ask that you make some allowance for having my tongue caught in my cheek.




Being technologically inclined (read: I’m a geek), I can tell you that the cell phone and laptop births don’t have anything to do with traffic jams. First, both are illegal to use in traffic jams in most states and provinces, and second, there are a lot more compelling reasons for people to want their technology on the move than to be stuck in traffic. People with offices on the road, such as computer repair techs, need to have phones to communicate with their offices as well as a laptop to test equipment and connections. And ever since the first cell phones came out (being used by the military at first, like every cool gadget that uses satellites), people have been fascinated with bringing their contacts with them all over the world.

Just my two and a half cents 🙂



Greeting to all;
Reading your article, Sis Buxton, gave me several thoughts in the form of questions.
One, are the horrific traffic problems in our worlds metro cities the beginning of or the birth of the cell phone? People caught in the traffic problems needed a way to communicate to the outside world.
Two, what about the laptop computer? Once more people entangled within the bowels of miles and miles of unmoving traffic! These poor souls are given a way to complete work or once more to communicate with the outside world.
Just some questions from my old demented mind.


living in an urban area with out traffic is not possible. The point is that How to control this in some scientific way. ‘a mathematical model to show the impact of unexpected events’ is really a wonderful Christmas gift.


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