Metropolitan arterial thrombosis

Over the years I have lived in this city, my daily commute has ranged from a few minutes to a frustrating hour or more. Current employment and accommodation are conveniently located in the opposite direction to the major traffic flows on Shk Zayed Car Park, so I can usually reach the office in a comfortable 23 minutes or so.

Not so today. First mistake, thinking that a queue which only reached back half way up the Greens meant that traffic there was moving. Wrong. Half an hour after leaving the house, I joined the next queue, to join the Shk Z C P. Movement is slow enough to allow me to postulate a theory of traffic flow based on fluid dynamics, and conclude that it is a non-linear equation. That is, any road has a given capacity for flowing traffic, which is based on a number of variables such as width, surface quality, visibility and number of junctions/exits. In normal conditions, where the amount of traffic is less than this calculated capacity, traffic flows freely and well. However, as traffic volumes approach the limit of the least accommodating stretch of highway, something happens, a 'tipping point' where the behaviour of the traffic changes from one state to another. Imagine water flowing through a pipe, and the water turns to treacle. It doesn't just slow slightly, it alters its behaviour by a factor of 10 or more.

This 'step change' seems to occur on Dubai's roads, and to spread out wave-like from the point of the original congestion. There is another model, a 'wave theory' of flow which describes the manner in which the effect of a minor incident causing approaching drivers to apply their brakes will leave a clot in traffic flow that persists long beyond the life of the original incident - think of the number of times you have been stuck in traffic crawling towards the point of an earlier accident, now cleared, only to find yourself accellarating back to normal speed once past the now non-existent obstacle. This bunching effect also moves slowly back down the queue of traffic against the direction in which the traffic is moving.

And so today. Sh Z C P thrombotic from Interchange 5 all the way in to Dubai. Inventive drivers creating their own personal exit ramps from the main highway into Al Qoz. Interchange 3 at an unexplained standstill. Interchange 2 ditto. Think I'll be smart and duck behind Emirates Towers and come up the underpass on the other side. Fat chance. Our brave Boys in Green have closed the tunnel and are directing everyone down towards the Trade Centre Roundabout. Back into the queue.

Crawl back along Sh Z C P past the scene of much consternation, another high-rise construction fire, apparently confined to the top floors of the tower. Must have been spectacular in the pre-dawn light - there was a considerable amount of ash and debris still scattered across the highway, gamely being gathered by a crew of labourers ducking between the crawling lines of traffic. Get past that, and the final kilometre of highway to my office is blissfully free-flowing. What should have taken 23 minutes today entailed a drive of an hour and a half. Still, got lucky with a parking space...