Engineering, psychology, and a bus on stilts

This week I’m trying to clear up the loose ends of threads I began and never finished, and get rid of some of the draft posts that I started but never polished…

Last week I posted about tracked hovercraft and straddling buses — a tongue-in-cheek look at how through the ages engineers have proposed ever more overcomplicated engineering solutions in an attempt to manage our out-of-control transport problems.  I assumed that my learned readers would get the point without labour. very kindly picked it as one of their daily front-page features, though, which led to it receiving around 4,000 spam comments, including several dozen along the lines of “wow that bus looks awsum and wood solve all our problems make one for america!!!?! (p.s. here’s a link to my blog!!!11!)”.*

Well, actually my guess is that the straddling bus will be just another absurd transport solution that fails to achieve the things that it is designed to achieve.  The stated purpose of the bus is not to get cars out of its way, it is to get the bus out of cars’ way: the designers complain that the frequent stop-starting of buses means that they hold up the traffic behind.  It will probably fail to achieve much in the way of making car drivers’ lives easier because the designers are obsessed with engineering and don’t consider Motorist behaviour.

Here are a couple of random fascinating psychology factoids.  I wonder to what extent the bus backers have considered them in their models?

  • When you make road lanes just a little but wider — as you will surely need to do if you are to accommodate the bus safely — people drive faster.  They’re not doing it deliberately or rationally, perhaps not even consciously, they just do it.  It feels right.
  • Drivers slow down for tunnels, and things that feel like tunnels — tree-lined avenues and close high walls.  Even if there’s nothing telling them to, and no rational safety reason to do so.  They just do it.

The cause of traffic jams is traffic.  Too much of if, behaving erratically.  We like to pretend that it’s bad engineering, because we can always fix engineering by replacing it with some different engineering.  And we like to pretend that it’s not the volume of traffic and the behaviour of drivers, because acknowledging this would mean giving up hope that one day the traffic jams will magically be solved.  But that’s the way it is: too many cars, too badly driven.  The straddling bus will probably not help congestion — at least, no more than a conventional bus on a conventional bus lane — because it will change driver behaviour in a way we can’t easily predict, but which (as described) will likely involve them slowing down and speeding up in chaotic waves as the bus passes them and they pass the bus.  It doesn’t sound like much, but these effects have a habit of amplifying themselves: the traffic between lanes will cease to be smooth, so cars will be changing lanes more, and this lane-changing contributes further to slowing things down, and also greatly raises the risks of accidents occurring.

Perhaps that effect will be marginal given all of the other existing complications and currents in the traffic flow.  Perhaps we’ll see other interesting unforeseen behaviour changes in the Shenzhen trial.  All that we can say for sure that everybody will be predictably surprised when drivers don’t behave in a simple rational manner.  Just like they were the last ten thousand times the solution to congestion was discovered.

The main reason the bus will fail, though, is the same reason that all urban roadspace provision schemes fail: create a new space for cars to drive in, and an equal or greater quantity of car journeys will be created to fill that space.  The cause of traffic jams is too much traffic.  Double the capacity for traffic and all you’re doing is doubling the size of the traffic jams.

Put a conventional bus on a conventional (parking and taxi enforced) bus lane.  It’s easier.

* Not that I’m not grateful for all your valuable contributions to our discussions ;)


One response to “Engineering, psychology, and a bus on stilts

  1. Pingback: Tweets that mention Engineering, psychology, and a bus on stilts | At War With The Motorist --

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