Traffic was literally at a standstill today

It was an unbelievable day. It took me 2 hours to get to work this morning when it ordinarily takes me just 45 minutes and that with the usual morning congestion. And on my way back from the hospital after visiting someone there, it took me 1½ hours to get home when it would just take half an hour. 

The commute back was longer than usual because there were road works in the route I took. But the morning traffic was unusual. 

The Star Online carried the news: Unusually bad traffic jam Tuesday morning. It said that, "The main cause of the congestion could not be determined." I however think it is because of the weather. It was raining, though not heavily but as the usual traffic slows down, it affected the entire system.

I remember reading in The Economist some years ago that any delays in traffic would cause further delays time four, if I am not wrong. For example, if a car was stalled at the middle of the road for 10 minutes would cause a traffic jam that will last for 40 minutes. I could not find the article now and so I could not confirm it as fact.

But I found this article which may just explain the unusual traffic congestion this morning: Traffic jam mystery solved by mathematicians. 

It says that, "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...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...When you tap your brake, the traffic may come to a full stand-still several miles behind you. It really matters how hard you brake - a slight braking from a driver who has identified a problem early will allow the traffic flow to remain smooth. Heavier braking, usually caused by a driver reacting late to a problem, can affect traffic flow for many miles."

I believe this was what exactly happened this morning because of the rainy weather. 

pearlie