So that's why we have traffic!!

Writing a blog is weird. You write it, you post it and then you just hope that some people might read it. And if you're really lucky, those reading it might even pay attention to it. And if you're really really lucky, they might even comment or send you a personal note or email.

Well, call me lucky. My last blog wrestled with the infuriating nature of traffic on the 401 and the infuriating part to me was my lack of understanding. Why the hell does it happen?

Well, when you have cousin doing a physics PHD at Harvard, you can sometimes get answers to things you don't understand. And then you feel stupid.

Gilad, you have earned your mention in today's edition of the blog.

Keep in mind, the following is written by a Montrealer, hence the anti-Ontario sentiment in #1. The rest of material is actually very smart and interesting.

You can read the explanation here:

There are three likely possibilities:
1. You're in Ontario, which means people don't know how to drive... therefore weird things happen.

2. The road width changes. If you go from 2 lanes to 3, then suddenly traffic can move faster. (If this isn't obvious, put a narrow tube at the end of a long one, and you'll see that the water flows faster out of the narrow tube than it flows through the big one). On a related note (which will also be related to point 3), when you lose a lane, traffic increases since the road is now narrower, but after a few kilometres, once people get over the whole merging jam, traffic could start to flow smoothly again even if you still have less lanes. (This is called a steady state solution... at the boundary where you lose a lane, traffic starts... but away from the boundary, people figure out how to drive faster and deal with the missing lane).

3. The most interesting point: a "domino effect" or "butterfly effect", etc. Imagine a line of cars, all cruising at the same speed.
Car 1 taps his breaks.
Car 2 sees car 1's break lights, but by the time he processes it, he needs to tap his breaks a little harder than car 1 did so as not to crash into him.
Car 3 sees car 2's break lights, but again because of his delay, needs to press a little harder than car 2 did, which is even harder than car 1's breaks.
....
.....
Car 1000 slams on his breaks, because of all the time delays.
So... let's consider 2 lanes now. Car 1 switches lanes (and probably slows down a little).
Car 2 sees him moving, and taps his breaks.
Car 3 sees the breaks, has a short delay, then presses his own breaks, etc....

Conclusion: Even though there wasn't an accident, if there are lots of cars to begin with, and someone at the front is switching lanes and / or keeps tapping the breaks, then it could lead to more traffic further behind.
When traffic cleared, it's likely that the leaders of the pack causing the trouble had gotten off at the exit before (or started driving normally).

That's how it's possible to have traffic out of nowhere.

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Alright, Gil, if you can solve that, can you figure out the opposite? As in the lack of traffic to my blog? Boo ya.

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Sign I'm approaching 30: I'm interested in traffic.