Going With The Flow

Another Bank Holiday is upon us and the newspapers are full of gloomy predictions of the  ensuing traffic chaos as optimistic Brits hope to grab a last piece of summer, weather permitting of course.

A psychologist advises that the only way to deal with road works and traffic jams is to accept that it’s beyond your control and that it’s all part of the holiday.  I imagine that parents of young children, for example, could be one group of travellers who may well disagree.

There is however a piece of research about those inexplicable traffic jams that have no discernible cause – and it makes interesting reading.A Japanese study has shown that there is a ‘critical density’ of traffic, estimated at 40 vehicles per mile of road.  Fluctuations in driving will lead to a jam, (even without an obstruction) once this critical density is exceeded and the traffic flow becomes ‘unstable’.

A fluctuation is simply that one driver, feeling that he is a little too close to the car in front will slow, and slightly overcompensate, braking too much.   The driver behind in turn, overcompensates slightly too, resulting in a disruption to the traffic flow.  The disruption then builds into what’s termed  ‘stop and go waves’

Cars eventually reaching the front of the jam will gain speed again, while new cars are continually joining at the rear.  Interestingly the stop and go waves are calculated at travelling back through the jam at 12mph, irrespective of the speed limit, although of course all cars are continually moving forwards.

The study shows that the critical density is the same the world over, so it may be some consolation to know that we’re not alone in our frustration on this particular weekend, or any other.

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