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| SCIENCE & TECHNOLOGY |
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Can maths keep us moving? Prof Yash
Pal This universe Trends |
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Can maths keep us moving? Here is a sobering thought: it is estimated that there are more than 750million vehicles on the planet, and that this mechanical population is swelling by more than 50m newcomers each year. At the current rate, the total number of cars on the road will double by 2025. All those vehicles need to go somewhere — but, increasingly, they don't.
While the combustion engine brings movement to the masses, and gives us the freedom of choice to live and work where we want, it also regularly leaves us gridlocked, sitting impotent and immobile in traffic jams, gently simmering in our own frustration. Congestion is nothing new. Archaeologists have discovered evidence of horse-and-cart jams in the ruins of Pompeii. But, health implications aside, traffic congestion is more than ever having a huge economic impact. In the UK, jams cost the national purse £20bn-£30bn a year. In America, it is around £65bn, and in n Moscow, now regarded as the most congested business city in the world, jams cost some $12bn a year. In the face of this global gridlock, road planners and traffic controllers are increasingly turning to science for solutions. As far back as the 1950s, mathematician Sir Michael James Lighthill was using wave theory to understand the complexities of traffic flow and interaction. Today the traffic-science sector attracts computer programmers, engineers and even astronomers, along with traditional mathematicians. With a tsunami of new motor vehicles already sweeping across developing nations such as China and India, and road capacity full in Europe and America, research into road-network optimisation is vital to keep the planet moving. Today's jambusters arm themselves with powerful computer-simulation tools to construct virtual highways containing thousands of virtual vehicles which interact with each other and gives clues as to why seemingly random congestion occurs. Although roads carrying vehicles at a certain density will always become congested, traffic scientists puzzled for years over those annoying jams that occur on free-flowing roads for no apparent reason. In the mid-90s, researchers in the US first built simulations which mirrored this effect. Within the computer programme, virtual cars would organise themselves spontaneously into distinctive patterns. Other models found a similar effect, where vehicle flows turned suddenly sluggish and stopped, as if they had crystallised. The commonly held view was that these patterns were caused by sheer weight of traffic. Boris Kerner, a researcher working at the Daimler Chrysler Research Centre in Germany, studied the traffic state between freely flowing cars and a full-scale traffic jam, which he called "synchronised traffic flow". He discovered that on carriageways where the traffic was moving in this manner vehicles appeared to have jelled into a type of unified, moving mass. This condition allowed waves of dense traffic to pass upstream along a motorway. More recently, a team of mathematicians from the University of Exeter discovered that these congestion waves were not due to sheer weight of traffic, but were down to driver action. The Exeter team developed a computer model that simulated the impact of unexpected events on motorways, such as lorries changing lanes. They discovered that under certain conditions, when cars are bunched in a specific density and travelling at a specific speed, a single driver over-reacting can set off a braking shockwave that will build momentum and travel back along a motorway for miles. As the initial driver brakes, the car behind has to brake, and so on until cars bunch into clumps and stop-start congestion develops. Eventually, several miles back, traffic grinds to halt. Researchers in Japan observed a similar "wave" pattern when they put 22 vehicles on a 23-metre, single-lane circuit and asked drivers to cruise steadily at 30km an hour. Initially the traffic moved freely, but small fluctuations soon appeared in distances between cars and built into larger pockets of congestion. These clusters, which scientists call "jamitons", spread backwards through the traffic like a shock wave. According to Tim Rees, head of traffic behaviour at research and development consultancy Transport Research Laboratory (TRL), major city road layouts have a lot to answer for. "Any city serviced by motorways which merge as they approach it will be prone to congestion," he says. TRL developed the traffic management system that controls the flow on the London orbital M25 motorway. This system, one of the most advanced in the world, uses real-time data collected from monitors on the carriageway and analysed by TRL experts to set strategic variable speed limits to try to alleviate problems before they materialise. As traffic builds to conditions where waves are likely to form, controllers set speed limits to regulate traffic flow at either 60mph or 50mph. Further back, a 40mph limit is set at the rear of the predicted congestion zone to help regulate traffic through it. However, even with the best technology in the world, sometimes demand on roads is just too high and jams are unavoidable. According to Gabor Orosz, assistant professor of mechanical engineering at the University of Michigan and one of the architects of the Exeter University study, the solutions lie in marrying macro-level systems, like the M25 variable speed limit system, with micro-level technology built into cars. He says: "In our research we discovered there is a region between a smooth-flowing state and a jam state where congestion build-up depends on the driver behaviour. “If you build radar into the bumper of a car and have an on-board computer that can control braking and acceleration, you can control the car through this type of traffic profile to optimise the chances of avoiding congestion. We tell the computer how to drive and the computer reaction time is much faster and more proportionate than a human's. It is like an auto-pilot system, but with limited capability. We call it Automatic Cruise Control. In theory an ACC car would get to a congestion area and signage would advise the driver to enable the ACC, which would take the driver smoothly through the zone." Until we can entrust our computer-controlled cars to smooth out the traffic however, the best advice scientists have to alleviate jams is to drive smoothly and steadily.
Alternatively, of course, you could just take the train. —
By arrangement
wit The Independent
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This universe On the other hand you find that the planets of the solar system do not twinkle. This is because a planet image has a width such that all the rays coming from it towards our eye are never bent away at the same time. |
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Trends WASHINGTON: Can money really make you happy? Not really, but up to about $75,000 a year can ease the pain of life's stresses, U.S. researchers have reported. A survey of 1,000 Americans shows they are overall fairly happy, and more money equals more satisfaction up to a point, Daniel Kahneman and Angus Deaton of the Center for Health and Wellbeing at Princeton University in New Jersey found.
Great apes protected in EU BRUSSELS: Primates, including mankind's closest relatives-chimpanzees, gorillas, bonobos and orangutans- have gained new protection after the European Parliament backed a clampdown on animal testing. "The use of non-human primates should be permitted only in those biomedical areas essential for the benefit of human beings, for which no other alternative replacement methods are yet available," a new EU law said. —
Reuters |
Stars are like point sources of light because they are so far. If a line joining a star to iris of your eye is uninterrupted, you would see the star continuously and there will be no twinkling effect. However the straight beam of light from the star is often bent away due to density fluctuations in the atmosphere. When this happens the star seems to scintillate — it twinkles.