How to Suppress Traffic Flow Instabilities

At high densities, traffic does not flow smoothly. Unsmooth flow decreases throughput, increases stress and wastes energy.

Click on the following to see some sample records, mostly collected on Interstate 93 going North from Boston:

Flow instabilities are predicted by many models — including “car following” models. Interestingly, the otherwise sensible rule that, for safety reasons, the separation between cars should be some multiple of the speed (e.g. one car length per 10 mph), assures instability. But more important here than explanations of why these instabilities occur is whether — and how — they can be suppressed. The answer is “yes” and the method is “bilateral control.”

Click on the following for a set of slides with a brief explanation of the problem and its solution:

Downloadable java application for simulation of traffic flow

For a simulation of the “car following” model and of “bilateral control” click on the following:

Download and run the “Traffic.jnlp” file. Java will start and you will get the control panel shown above (*)
Click the “Start” button. Observe the instabilities develop (below, left)
Then check “Bilateral Control” and see the dissolution of those instabilities (below, right):

For additional details, see the paper:

B.K.P. Horn, “Suppressing Traffic Flow Instabilities”
IEEE Intelligent Transportation Systems Conference (ITSC 2013)
Den Haag, Netherlands, 2013, October 6-9.

(*) To run the simulator you may have to add this web site to the Exception Site List.
In Windows, for example, go to the Control Panel, click on "Java", select "Security",
then click "Edit Site List" and add "" to the list (See video instructions, thanks to Liang Wang).
Berthold K.P. Horn,