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Metro Monday: Shockwave Theory Explained

Published
by
Gabriel Lopez-Bernal
on March 17, 2008
in Congestion, Highway, Shockwave Theory and Traffic
.
If you’ve ever been driving along the highway and suddenly everything comes to a dead stop or a slow down for no apparent reason you’ve been caught up in a shockwave traffic jam. The Mathematical Society of Traffic Flow in Japan has created this video to illustrate the shockwave phenomenon. In Miami, you’ll typically find yourself in one of these heading on US-1 southbound just after I-95 (a spot where you should likely be riding metrorail instead…)

4 Responses to “Metro Monday: Shockwave Theory Explained”

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  1. 1 Eli Sokol
    Mar 17th, 2008 at 3:12 pm

    Very interesting experiment. Based on the results of this project, would it be wise to strictly enforce a minimum speed limit in areas with few to zero stoplights such as a highway or the beginning of US 1 south bound?

  2. 2 Ryan Sharp
    Mar 17th, 2008 at 4:43 pm

    Eli,

    Enforcing a minimum speed limit would only encourage people to go faster (something we definitely don’t need to encourage) which is bad for a number of reasons. First, it would decrease the capacity of the roadway because each individual car would be taking up more space. Secondly, it’s at faster speeds that you get more quick braking and sudden maneuvers that ripple traffic backwards like the shockwave. Third and most importantly, it would compromise the pedestrian realm, which would suffer from people driving faster. If anything, we should be lowering speed limits and more strictly enforcing the limits. I believe the main point of this video is to show how little it takes to start a traffic jam, which is just another reason why transit is superior to highways and thus it’s where our investments should be going.

  3. 3 Eli SOkol
    Mar 17th, 2008 at 7:51 pm

    Well said, I hadn’t thought of it that way. Is this to say though that there really is no solution to traffic? I’d like to believe that there is a practical solution to traffic, though I by no means am encouraging a auto-centered lifestyle. I just would like to believe that this problem is fixable on a wide scale. (exluding building alternative modes of transit)

  4. 4 JM Palacios
    Mar 17th, 2008 at 9:16 pm

    There are a few ideas that have come out to try to improve traffic flow due to shockwave related delays. One would be ramp metering, which is supposed to be turned on in Miami-Dade when the I-95 HOT lanes are up and running. (So not only will the express lanes help traffic flow, so will the ramp metering, and we won’t know which is more useful.) Basically all that does is reduce the volume of slow merging traffic, so mainline traffic can continue to flow.

    The best way to avoid such a delay is to eliminate human drivers. Automated cars would communicate with each other effectively to avoid sudden slowdowns and keep uniform speeds.

    To answer the question, though, Eli: there is no real solution to congestion. The rule is, you cannot build your way out of congestion. This is why transit becomes necessary, as it becomes the only affordable way to move lots of people once the roads are clogged with cars.

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