雅思阅读 94: High-Speed Rail's Quiet Carbon Reckoning（高铁的碳排账单）

改编自 Stanford University PH240 / Frontiers in Sustainable Cities（2025年）。雅思阅读 Section 3 难度，约 1050 词。 素材来源：http://large.stanford.edu/courses/2025/ph240/arora2/

Reading Passage

A. When governments announce a new high-speed railway, they almost always describe it as an environmental triumph. Gleaming trains, they say, will pry travellers out of aeroplanes and motor cars and deliver them to city centres at three hundred kilometres an hour, all while slashing the carbon cost of the journey. The arithmetic behind such claims is attractive on its face. A train seats hundreds, it runs on electricity rather than jet fuel, and a well-loaded carriage spreads its emissions across so many passengers that each individual trip looks almost guilt-free. Politicians have every reason to lean on this story, because railways are also jobs programmes, prestige projects and engines of regional development, stitching distant cities into a single commuter belt. Yet the carbon reputation of high-speed rail has never been as spotless as the brochures suggest, and a closer look at the numbers reveals a technology whose green credentials depend on three variables that its cheerleaders rarely mention: how full the carriages are, how the power was made, and how long it took to build the thing in the first place. Run badly, a celebrated railway can emit more than the aeroplanes it was meant to replace; run well, it is among the cleanest ways yet invented to move a thousand people across a continent.

B. Start with the case that the brochures actually make, because it is a strong one. Measured per passenger-kilometre and excluding the one-off cost of building the line, a fully occupied electric train emits between two-thirds and ninety-seven per cent less greenhouse gas than the same journey by air. On China's vast network, where the trains are extraordinarily busy, the figure has been estimated at roughly twenty-one grams of carbon dioxide for every kilometre a passenger travels; a domestic flight, by contrast, manages something like two hundred and fifty, and a private car on a congested motorway around a hundred and seventy. The advantage is not subtle. It arises because steel wheels on steel rails roll with far less resistance than rubber tyres on asphalt, and because a single electric motor drawing hundreds of people is inherently more efficient than hundreds of separate internal-combustion engines. Replace enough short-haul flights with fast trains, the logic runs, and aviation's sprawling emissions would shrink overnight, freeing the runways for the long-haul routes where flying is irreplaceable. On busy corridors, where a train can leave every few minutes and walk straight into the city centre, this substitution already happens of its own accord.

C. The first hidden cost is the railway itself. Laying hundreds of kilometres of track, boring tunnels across mountain ranges, building viaducts over valleys and forging a thousand tonnes of steel rail consumes enormous amounts of cement and energy up front. One assessment estimated that constructing California's planned five-hundred-kilometre line would release close to ten million tonnes of greenhouse gases before the first ticket was ever sold. The second complication is the source of the electricity. A train is only as clean as the grid that feeds it: where the power comes from coal, as much of China's historically did, the per-kilometre advantage narrows sharply, even if it rarely disappears entirely. Advocates respond that grids decarbonise over time while the concrete and steel of a railway last for a century, so the debt paid on day one is gradually forgiven by decades of clean running. The payback period, they argue, is not a reason to delay but a reason to build now, before the cheap low-carbon power arrives. A railway built today, in other words, can be forgiven its day-one debt by the clean electricity it will draw for the rest of the century.

D. Beyond conventional wheeled high-speed rail lies a cousin that promises to push efficiency further: magnetic levitation. Instead of rolling on steel wheels, a maglev train is hoisted millimetres above its guideway by attractive and repulsive magnetic forces, driven by a linear motor laid in the track. With no physical contact, there is no friction to overcome and no wheelsets to wear out, which is why proponents argue that a mature maglev system should produce between fifteen and twenty per cent less carbon per passenger than even a modern conventional railway, and sixty to seventy per cent less than flying. The ride is also quieter and smoother, since there is neither rail noise nor the vibration of wheels pounding joints. Critics note that the guideway itself is extraordinarily expensive to build and that the handful of operational lines have yet to prove they can fill their seats at scale. The technology is therefore often promoted less as a replacement for today's trains than as an upgrade that may, in time, let them run faster and more quietly, retrofitted onto existing corridors where demand justifies the extraordinary price of a new guideway.

E. Behind all these engineering debates sits a quieter truth: occupancy matters more than the machine. A near-empty high-speed train is a travelling environmental catastrophe, burning almost as much energy to move fifty people as to move five hundred. A study of the Haramain line in Saudi Arabia found that underused services could emit more greenhouse gas per year than the buses they were meant to replace; conversely, when the trains ran full and drew on renewable electricity, the same railway delivered savings measured in hundreds of thousands of tonnes. The lesson is uncomfortable for planners. A railway's carbon benefit is not a property of the tracks alone but of how many people choose to ride them, and whether the electricity feeding them gets cleaner. Off-peak fares and sensible pricing can keep the seats filled; running a prestige train half-empty is, in carbon terms, little better than the flights it was meant to replace. Prestige alone, it seems, does not guarantee green.

Questions 1-4

Choose the correct heading for paragraphs B, C, D and E from the list of headings below.

List of Headings i. Why a full train beats flying on paper ii. The history of railway electrification iii. The two hidden costs that the brochures omit iv. How maglev suspends its way to greater efficiency v. Ridership — the variable that decides everything vi. Why private cars will always remain superior vii. The commercial airline industry's lobbying power

1. Paragraph B: ____
2. Paragraph C: ____
3. Paragraph D: ____
4. Paragraph E: ____

Questions 5-8

Choose the correct letter, A, B, C or D.

5. According to the passage, a fully occupied electric train, measured per passenger-kilometre, A. is always dirtier than a private car. B. emits far less than the same journey by air. C. produces identical emissions to a flight. D. depends entirely on jet fuel.

6. What does the writer identify as the "hidden" cost? A. The salaries of train drivers. B. The embodied emissions of building the line and the cleanliness of the power grid. C. The price of tickets in rural areas. D. The noise complaints of residents.

7. What advantage does maglev technology offer over conventional rail? A. It requires no electricity at all. B. It uses magnetic forces to eliminate wheel contact and friction. C. It can be built more cheaply than a motorway. D. It carries freight more efficiently than lorries.

8. The Haramain line study suggests that a railway's environmental benefit ultimately depends most on A. the speed of the train. B. how many passengers actually ride it and how clean the grid is. C. the colour of the carriages. D. the number of stations built.

Questions 9-13

Do the following statements agree with the claims of the writer?

Write:

• TRUE if the statement agrees with the information
• FALSE if the statement contradicts the information
• NOT GIVEN if there is no information on this

9. A busy electric train on China's network was estimated at roughly twenty-one grams of CO2 per passenger-kilometre.
10. Constructing California's planned line was estimated to release almost ten million tonnes of greenhouse gases.
11. A near-empty high-speed train is an unusually efficient way to travel.
12. Maglev trains are currently cheaper to build than conventional railways.
13. The first commercial high-speed railway in the world opened in Japan in 1964.

Questions 14-15

Complete the summary below using NO MORE THAN TWO WORDS from the passage.

A maglev train floats just above its guideway on (14) __________ forces and is propelled by a linear motor, removing the (15) __________ that a wheeled train must overcome.

答案与解析

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