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TG reveals the truth behind traffic

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When it comes to traffic, the experts are pretty much in agreement on one issue: we should really behave more like ants. Since they first crawled from under a leaf and marched nose-to-tail along the nearest stick, they’ve accepted the single unavoidable truth about traffic - we’re all in it together. Each ant sets his speed for the benefit of the colony, not for his own amusement. No late braking. No overtaking. No slinging of expletives when Ant A cuts in front of Ant B at the last minute, or follows too closely to his little anty bottom.

We, on the other hand, have only had a hundred years or so to get the hang of moving in the same direction together at speeds we weren’t designed for… and with limited room (even if we use only our fair share of the road, we’re acting against the interests of the whole by depleting the common resource - roadspace). Then we have to deal with the frustration of other phenomena: why does one lane appear to move faster than the other? Why does the red light last longer than the green? And why the hell has this traffic stopped for no apparent reason?

People have been trying to get their brains around this for decades. There are traffic engineers, traffic professors and even traffic psychologists - people who’ve devoted entire careers to the problem, yet we still don’t fully understand why it happens or how to fix it. Sure, building a new road or two might help - though some studies refute this - as does opening the hard shoulder to traffic in rush hour. And as we’ll see later on, better use of traffic lights goes a long way to unclogging urban jams. But there’s no one, simple fix.

At the heart of the matter is one measurement: flow. There’s even an equation for it, expressed as Q = KV, where Q equals the flow of traffic, K the density of vehicles and V the speed of vehicles. Other people use metaphors involving water passing through holes in buckets, or rice being tipped into a funnel. Many have collected vast quantities of data and built algorithms to forecast where congestion will occur and how to avoid it.

But as Tom Vanderbilt notes in his excellent and cunningly named book Traffic, “Even the most sophisticated models do not fully account for human weirdness.” To illustrate this, let’s use a classic scenario. There you are, driving along a free-flowing motorway, when suddenly the traffic thickens and eventually comes to a stop. Ten minutes later, it starts to move again, and so you look for the idiot who’s crashed, or for the broken-down Peugeot. Alas, there’s nothing, and you’ve wasted all that time for no reason whatsoever. Or so you think.

In one experiment, a Japanese traffic professor asked several drivers to follow each other around a circle at a steady 30mph, keeping a consistent gap to the car in front. After just a few minutes, the order began to break down, as slight decelerations sent a shockwave back around the circle until eventually it was crawling along at barely a few miles per hour.

Now picture that circle, straightened out and stretched along a motorway. Those slight changes in speed could be someone hesitating for a moment, fiddling with the stereo, or picking up an old Twiglet from the footwell. To account for this, the car behind is forced to slow, and the one behind that. The wave ripples back down the road at a speed of about 12mph, until following traffic is at a standstill while that bloke further up the road enjoys his leftover wheat-based snack.

As Vanderbilt puts it, “The hiccup in heavy traffic that passes through you might be the echo of someone who, forward in space and backward in time, did something as simple as change lanes.” Or in other words, you don’t drive into the jam - the jam drives into you.

And there are other things to think about. The weather, for example, which can throw up optical illusions. Then there’s the psychological and physical elements - we’re all in different moods with different energy levels, some have better eyesight than others, some are in old cars and some are in new ones that make 90mph feel more like 60mph. Some simply believe they should be in front of you because they are awful humans that still exist in some feudal bubble. See the problem?

And that’s just a small part of the issue. Sometimes there are just too many people using the same piece of road, so it becomes saturated. Literally soaked in traffic. And that’s before we’ve even looked at roadworks and route closures and anything else that gets in the way of a pleasant journey.

In the distant future, we might all be passengers in an autonomous convoy that moves around like an especially ordered school of fish, but even then - if everybody left at a similar time with a similar destination - there would still be congestion. But there is hope. Granted, we will not turn into genetically modified, ant-like travellers any time soon, but as our understanding of traffic improves, our life on the road will become more liberating. Driving is not dead. You just have to know where to do it…

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