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Traffic Flow is such a fragile thing

(12 posts)
  • Started 8 years ago by Wilmington's Cow
  • Latest reply from Edinburgh Cycle Training

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  1. Wilmington's Cow
    Member

    Heading to work today along the Glasgow Road, traffic was backed up hideously heading west all the way from the PC World roundabout. It appears the cause was a large car transporter stopped at the Jag garage further along, because beyond it there was no queue, and virtually no traffic.

    Seems weird that something parked in the non-usual-traffic bus lane can cause such a massive tailback, but it definitely was. Can there really be that many buses and taxis shuffling out to pass the obstruction to cause that much of a ripple backwards?

    Posted 8 years ago #

  2. kaputnik
    Moderator

    There was a fairly large tailback around the Forestry Commission / Zoo area, caused by a lorry delivering to the building site of the old Barnardos Home that had parked facing-traffic half across the bus lane and entirely across the pavement. This meant all vehicles using the bus lane had to squeeze into the other lane before squeezing back out to get to the bus stop on the other side.

    Posted 8 years ago #

  3. Charlethepar
    Member

    I was once told that the nearest analogous model to traffic flows is fluid dynamics, where big waves can be created by small perturbations.

    A quick wiki education gives me:-

    "Traffic phenomena are complex and nonlinear, depending on the interactions of a large number of vehicles. Due to the individual reactions of human drivers, vehicles do not interact simply following the laws of mechanics, but rather show phenomena of cluster formation and shock wave propagation, both forward and backward, depending on vehicle density in a given area."

    https://en.wikipedia.org/wiki/Traffic_flow

    What it should add, of course, is ".. unpredictable, inconsistent and often selfish human drivers..."

    In my experience, any situation where traffic has to merge lane gives rise to all sorts of weird behaviour, with some drivers remarkably patient, letting in others who have obviously chanced it and passed them on a clearly blocked lane. This just winds up others in the queue for the continuing lane, who then become determined to let no one in. And so it goes on.

    Posted 8 years ago #

  4. Wilmington's Cow
    Member

    That makes sense, reminds me of a programme I watched once on motorway driving and some research that was being done (in Japan I think?) and the benefits of those bits of road with 'keep two chevrons clear to the car in front' where the traffic flowed without the stop/start wave.

    Posted 8 years ago #

  5. kaputnik
    Moderator

    I seem to recall a cool video (Japanese again I think) shot from a bird's eye position of lots of cars driving around, equi-spaced in a big circle on an empty lot and then one of the cars is made to slow down and it nicely illustrates the wave that propagates through the rest of the cars following behind.

    Posted 8 years ago #

  6. Stickman
    Member

    @kaputnik

    This is the one:

    [+] Embed the video | Video DownloadGet the Flash Videos

    Posted 8 years ago #

  7. kaputnik
    Moderator

    In my experience, any situation where traffic has to merge lane gives rise to all sorts of weird behaviour,

    The ambiguous lane markings just before and after the first westbound bus stop on York Place demonstrate this nicely. People are trying to merge in to the left as they come off the roundabout only to find a bus stopped in the lane ahead and so try and move out right again only to then repeat the merge to the left beyond the bus. People act in a random manner and choose different ways of trying to best get through this section of road and the upshot is usually a gridlock of randomly intermeshed vehicles that you have to pick your way around.

    Posted 8 years ago #

  8. Wilmington's Cow
    Member

    "People act in a random manner and choose different ways of trying to best get through this section of road and the upshot is usually a gridlock of randomly intermeshed vehicles that you have to pick your way around"

    Ain't that the truth.

    If I'm in the car heading to that point I try to plan ahead (as far as possible) by looking to see if there are any buses about to get there. If there are then I go round the roundabout on the inside, if not then round on the outside. Works a treat, though also involves there being light enough traffic to change lane on approach. Also involves looking at the road ahead and planning, rather than staring at the end of your bonnet.

    Posted 8 years ago #

  9. chdot
    Admin

    Just looked at the video above, this came next -

    [+] Embed the video | Video DownloadGet the Flash Videos

    Posted 8 years ago #

  10. neddie
    Member

    A mere 20 years ago, all that would've been bicycles

    Beijing - the city that swapped a perfectly good transport system for a perfectly useless one

    Posted 8 years ago #

  11. Min
    Member

    Clearly what they need is to widen that road. Those narrow medieval Chinese streets are what is causing the problem.

    Posted 8 years ago #

  12. Edinburgh Cycle Training
    Member

    This morning, right at the lights exiting Waterloo Place onto Princes Street, a wagon parked to unload. It carried its own forklift truck to do so.

    When I arrived (on my bike) big tailback up WP, but also on the junction as the FLT driver was on the other side of the road, waiting to cross the W/B lanes to get to his wagon.

    Oh how I smirked as I filtered through dozens of horn tooting motors

    Posted 8 years ago #

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