Why do traffic jams occur?

By Nathan Dyck

You’re cruising on your way to school, making good time, when suddenly *bam,* you’re in the middle of a traffic jam.

Transportation problems are as old as mankind, and we see more and more problems as our cities become increasingly crowded. But as long as we drive cars, we’ll have traffic.

"People should be prepared for longer and longer delays, whether or not we have a working transit system," said University of Calgary Civic Engineering professor Dr. J.F. Morrall. "If we all lived in 20-storey apartments, we could probably make transportation more efficient."

But he doesn’t think this will happen, because of lifestyle preferences and willingness.

"This is a very spread-out city… you can’t replace the automobile very easily," he said.

So, do we need to build bigger roads to handle more traffic?

"This city designs its road systems right at capacity… this doesn’t give us any cushion," said Morrall. But road capacity isn’t everything, and looking at it straight-on isn’t best: building a road from A to B, and making it big enough to fit the right number of cars may not be that effective. Despite this, a study on traffic congestion funded by nine State departments in the U.S. concluded tactics used include "add road space" and "lower the number of vehicles."

According to Dan Bolger, who is responsible for Coordinated Systems Planning of the City of Calgary, the city takes demographic and land-use patterns and tries to make a model of what roads are needed and where, and tries to encourage people to use other forms of transportation. He admitted, however, that as a part of their stated policy, "[there] may be situations where we can’t handle the demand." He suggested commuters "just try and live with it."

New ways of looking at traffic behaviour and road use may explain what causes many problems. The visualization of traffic as a flowing gas has proved to be useful. It explains many situations and events in real-world traffic; phenomena not accounted for in the strictly linear classical techniques.

According to Morrall, "the saturation flow of a traffic lane is about 1,600-1,800 vehicles per hour of green." When more vehicles are added to this mix, they develop queues, and these queues form a shockwave and ripple-back effect. When a flowing gas enters a bottleneck, it becomes compressed as the molecules begin to crowd together. Each molecule can be viewed as a car, except molecules are never late for an appointment. The shock wave travels upstream.

These bottlenecks aren’t necessarily traffic lights or burning wrecks. Systems engineers describe "ghosts," which can cause breakdowns in the flow for hours after the initial problem is gone.

Imagine driving down the highway and Bozo the clown steps in front of you. You swerve and manage to only nick his big red shoe. This is termed an "incident." However, when you swerve, you cut off someone beside you and they come to a stop. The person behind them also comes to a stop, and the one behind them jams on his brakes. The flurry of cars stopping and starting travels back up the highway. The effects of this can linger in the right traffic conditions, and hours later, cars are still slowing down, even though the cars at the front are free to speed up again once they have cleared the "ghost" of Bozo.

Other times, there is no clown to blame. In any system that contains many parts, each part affects the others. Tiny fluctuations can grow in huge and unpredictable ways.

One way to see this is to imagine some dogs on a log in the middle of the river. If one dog moves, it sets up a disturbance, forcing the other dogs to move to keep their balance. Pretty soon the log is rocking violently and many of the dogs may get wet. The expanding network of roads and lights designed to try and keep up with demand may not always be helpful, since drivers aren’t making rational decisions and add to problems. Increased capacity in a limited area often works only to pile more dogs onto the log.

Strangely, it is often when the traffic is densest that it flows smoothest. There are often fewer starts and stops backlogging the road, and less jostling for position, which adds less chaos to the flow.

 

15 comments

  1. Thanks for another informative web site. The place else mayjust I get that type of information written in such a perfectapproach? I’ve a undertaking that I am just now working on, and I’vebeen on the look out for such info.

  2. Do you mind if I quote a couple of your posts as long as I
    provide credit and sources back to your site? My website is in the very same niche
    as yours and my visitors would definitely benefit from some of the information you present here.
    Please let me know if this alright with you. Cheers!

  3. This is the perfect web site for anyone who wants to understand this topic.

    You know a whole lot its almost hard to argue with you (not that I actually will need to…HaHa).
    You certainly put a brand new spin on a subject that has
    been written about for decades. Excellent stuff, just great!

  4. Hmm it seems like your site ate my first comment (it was super long) so I guess I’ll just sum it up what I submitted and say, I’m thoroughlyenjoying your blog. I as well am an aspiring blog writer but I’m stillnew to the whole thing. Do you have any recommendations fornewbie blog writers? I’d genuinely appreciate it.

  5. whoah this weblog is great i love studying your posts.Stay up the good work! You recognize, many people are looking around for thisinformation, you could help them greatly.

  6. With havin so much content do you ever run into any issues of
    plagorism or copyright infringement? My site has a lot of unique content I’ve
    either created myself or outsourced but it looks like a
    lot of it is popping it up all over the web without my permission. Do you know any ways to help
    stop content from being ripped off? I’d genuinely appreciate it.

  7. I quite like looking through an article that can make men and women think.Also, many thanks for allowing for me to comment!

  8. Great post. I was checking continuously this blog and I’m impressed!Very helpful info specifically the last part 🙂 I care for such information a lot.I was looking for this particular information for a very long time.Thank you and best of luck.

  9. Awesome issues here. I’m very satisfied to peer your article.
    Thank you so much and I am taking a look ahead to contact you.
    Will you kindly drop me a mail?

  10. Everything posted made a ton of sense. But, think about this, what if you were to write a awesome title?I am not saying your information isn’t good, however suppose you added something that makes people want more?I mean Este viernes inicia el censo de viviendas afectadas en Acapulco – Mar deNoticias Guerrero is a little boring. You could glance at Yahoo’s frontpage and see how they write post headlines to grab viewers to click.You might add a related video or a related pictureor two to grab people excited about everything’ve got to say.In my opinion, it might bring your blog a little bit moreinteresting.

Leave a comment