Chart of the Day: The Traffic Jam Nonlinear Flow Loop



This chart is basically a re-drawing of the one that I put up last week, depicting flow rate vs. density for a traffic jam. The difference here is that it depicts a non-linear time sequence, showing how traffic flow increases, destabilizes, and then falls into a separate “congested” regime with lower flow rates.

Coincidentally, it is precisely this kind of behavior that ramp meters seek to control. If ramp meters can keep flow rates from plummeting into the “post-critical” phase of the cycle, then everyone traveling on the freeway is better off. In other words, when it comes to freeway behavior, congestion is a one-way street (topologically speaking, of course).

PS Image comes from Philip Ball’s interesting book, Critical Mass.

Bill Lindeke

About Bill Lindeke

Pronouns: he/him

Bill Lindeke has writing blogging about sidewalks and cities since 2005, ever since he read Jane Jacobs. He is a lecturer in Urban Studies at the University of Minnesota Geography Department, the Cityscape columnist at Minnpost, and has written multiple books on local urban history. He was born in Minneapolis, but has spent most of his time in St Paul. Check out Twitter @BillLindeke or on Facebook.