# Has This Been Mathematically Analyzed? (Smooth vs. Bunched Traffic Flow) **URL:** \ **Category:** Factual Questions\ **Created:** [June 19, 2011, 8:00pm UTC](https://boards.straightdope.com/t/has-this-been-mathematically-analyzed-smooth-vs-bunched-traffic-flow/586062 "2011-06-19T20:00:20Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![ralph124c](https://avatars.discourse-cdn.com/v4/letter/r/8797f3/32.png) [@ralph124c](https://boards.straightdope.com/u/ralph124c)\ **Post date:** [June 19, 2011, 8:00pm UTC](https://boards.straightdope.com/t/has-this-been-mathematically-analyzed-smooth-vs-bunched-traffic-flow/586062/1 "2011-06-19T20:00:20Z")
While driving on Rt 128 yesterday, I was wondering about traffic flow on large multi-lane highways. In an ideal sitation, cars follow eachother at fixed distances (to allow for emergency stopping), and the road then has a certain capacity of cars/hour. then, all Hell breakes loose-somebody slows down in the passing lane, causing the traffic to “bunch up” this seems to propapgate, until the road becomes a sequence of bunches of traffic. I sspect that “bunched” traffic lowers the optimm road capacity, and also leads to dangerous driving (people weaving in and out). At any rate, can this be analyzed? Does bunching happen spontaneously, or is it a function of traffic density? ---
**Author:** ![Andy\_L](https://avatars.discourse-cdn.com/v4/letter/a/c67d28/32.png) [@Andy\_L](https://boards.straightdope.com/u/Andy_L)\ **Post date:** [June 19, 2011, 8:04pm UTC](https://boards.straightdope.com/t/has-this-been-mathematically-analyzed-smooth-vs-bunched-traffic-flow/586062/2 "2011-06-19T20:04:03Z")
Here’s an article on the subject with simulations, etc. [http://trafficwaves.org/](http://trafficwaves.org/) ---
**Author:** ![Gary\_Robson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gary_robson/32/3448_2.png) [@Gary\_Robson](https://boards.straightdope.com/u/Gary_Robson)\ **Post date:** [June 19, 2011, 9:17pm UTC](https://boards.straightdope.com/t/has-this-been-mathematically-analyzed-smooth-vs-bunched-traffic-flow/586062/3 "2011-06-19T21:17:55Z")
I enjoyed the book, _Traffic: Why We Drive the Way We Do (and What It Says about Us)_ by Tom Vanderbilt. It addressed the issue well. ---
**Author:** ![Asympotically\_fat](https://avatars.discourse-cdn.com/v4/letter/a/e47c2d/32.png) [@Asympotically\_fat](https://boards.straightdope.com/u/Asympotically_fat)\ **Post date:** [June 19, 2011, 9:58pm UTC](https://boards.straightdope.com/t/has-this-been-mathematically-analyzed-smooth-vs-bunched-traffic-flow/586062/4 "2011-06-19T21:58:15Z")
> [@ralph124c](#): > > While driving on Rt 128 yesterday, I was wondering about traffic flow on large multi-lane highways. > In an ideal sitation, cars follow eachother at fixed distances (to allow for emergency stopping), and the road then has a certain capacity of cars/hour. > then, all Hell breakes loose-somebody slows down in the passing lane, causing the traffic to “bunch up” this seems to propapgate, until the road becomes a sequence of bunches of traffic. > I sspect that “bunched” traffic lowers the optimm road capacity, and also leads to dangerous driving (people weaving in and out). > At any rate, can this be analyzed? Does bunching happen spontaneously, or is it a function of traffic density? Unfortunately i’ve pnly read a few articles on it a few years ago so I can’t offer much insight, but yes it has is answer. I don’t know whether there is a simalir situation in in the USA, but because of the studies of how they come about and how they slow the traffic down we have variable speed limits on the motorways in the UK. ---
**Author:** ![j666](https://avatars.discourse-cdn.com/v4/letter/j/9de0a6/32.png) [@j666](https://boards.straightdope.com/u/j666)\ **Post date:** [June 19, 2011, 10:08pm UTC](https://boards.straightdope.com/t/has-this-been-mathematically-analyzed-smooth-vs-bunched-traffic-flow/586062/5 "2011-06-19T22:08:39Z")
In the case of 128, the answer is obvious; two many curves. Too many hills. Also too many people on cruise control in the left lanes, and two many people determined to get over to those left lanes as soon as they get on. ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [June 19, 2011, 10:29pm UTC](https://boards.straightdope.com/t/has-this-been-mathematically-analyzed-smooth-vs-bunched-traffic-flow/586062/6 "2011-06-19T22:29:27Z")
[Kind of related post from Cecil- “The freeway has no stoplights, so why does traffic halt?”](http://www.straightdope.com/columns/read/28/the-freeway-has-no-stoplights-so-why-does-traffic-halt)