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A．mainly because the levels of carbon dioxide are rising
B．possibly because the ice caps in the poles are melting
C．exclusively due to the effect of the internal of the earth' s climate
D．partly due to variations in the output of solar energy
答案
更多“Although the fuel consumption is greater in the northern hemisphere, temperatures there se”相关的问题
第1题
By "crisis of comprehension" the author means that many students ______.
A．are too much. concerned with grades
B．fail to understand the real goal of education
C．lack proper practice in phonic and grammar drills
D．are unable to understand what they read, although they do reasonable well on standardized tests
第2题
听力原文： Although I think the United States generally has an excellent system of transportation, I do not think that it does a good job of transporting people between cities that are only a few hundred miles apart. A person commuting between Detroit and Chicago, or between San Francisco and Los Angeles, so-called "strip-cities", may spend only a relatively short time in the air while spending several hours getting to and from the airport. This situation makes flying almost as time-consuming as driving. Moreover, airplanes use a lot of their fuel just getting into the air. They are simply not fuel-efficient on short trips. High-speed trains may be an answer. One fairly new proposal for such a train is for something called "mag-lev", meaning a magnetically levitated train. Mag-levs will not actually ride on the track, but will fly above the track that is magnetically activated. This will save wear and tear on the track. These trains will be able to go faster than 150 miles per hours. At that speed, conventional trains have trouble staying on the track. As you can see, mag-levs offer exciting possibilities for the future.
(20)
A．Strip-cities.
B．Transportation of the future.
C．Energy conservation.
D．Advantages of air transportation over railroads.
第3题
Naturalgas Vehicles
Kermit the Frog once said, "It's not that easy being green." Although he wasn't referring to cars, his observation seems particularly appropriate for the auto industry today: Designing, developing and marketing "green" cars has not been an easy task, which is why gasolinepowered vehicles still rule the road and fossil fuels still ac count for almost 75 percent of the world's energy consumption. As gasoline prices soar and concern over harmful emission mounts, how ever, cars that run on alternate fuel sources will become increasingly important. A naturalgas vehicle, or NGV, is the perfect example of such a carit's fuelefficient, environmentally friendly and offers a relatively low cost of ownership.
Natural Gas Basics
The word "gas" is a confusing term because it is used to de scribe many different substances that are similar hut not exactly the same. For example, the "gas" you put in your car is gasoline, one component of crude oil, or petroleum. Petroleum is a dark, sticky liquid mixture of compounds formed underground by tile decay of ancient marine animals.
Natural gas also cranes from the decay of ancient organisms, but it naturally takes a gaseous form. instead of a liquid form. Natural gas commonly occurs in association with crude oil. It is derived from both land plants and aquatic(水中的) organic matter and forms above or below oil deposits. It is often dissolved in crude oil at the high pressures existing in a reservoir. There are also reservoirs of natural gas, known as nonassociated gas, that contain only gas and no oil.
Natural gas consists primarily of methane(甲烷) and other hydrocarbon gases. Hydrocarbons are organic compounds composed only of the elements carbon and hydrogen. The hydrocarbons in natural gas are called saturated hydrocarbons because they contain hydrogen and carbon bound together by single bonds.
Like gasoline, natural gas is combustible, which means it can be used in a combustion engine like gasoline. But cars that could burn natural gas didn't appear on the scene until the 1930s.
From Field to Ford
We extract natural gas trapped in underground reservoirs by drilling wells into the earth. A modem well, equipped with diamondstudded drill bits, can drill to depths approaching 25,000 feet.
Throughout the 19th century, the use of natural gas remained localized because there was no way to transport large quantities of gas over long distances. In 1890, the invention of a leakproof pipeline coupling made it possible to transport gas miles from the source, Improvements in pipeline technology continued over the next two decades constructed more than 10 major natural gas transmission systems in the United States, making natural gas a viable energy source for many applications. The oil shortages of the late 1960s and early 1970s brought renewed interest in natural gas as a fuel source, especially for automobiles.
Today, owners of naturalgas vehicles can fill up their cars at one of 1,300 fueling stations located in the United States. Honda al so offers a personal natural gas pump to people who purchase its naturalgaspowered Civic. The pump uses a home's existing natural gas lines and can be installed for $500 to $1500.
Naturalgas Vehicle Design
Naturalgas vehicles use the same basic principles as gasoline powered vehicles. In other words, the fuel (natural gas in this case) is mixed with air in the cylinder of a fourstroke engine and then ignited by a spark plug to move a piston up and down. Although there are some differences between natural gas and gasoline in terms of flammability and ignition temperatures, NGVs themselves operate on the same fundamental concepts as gasolinepowered vehicles.
Still, some modifications are required to make an NGV work efficiently. These changes are primarily in the fuel storage tank, the engine and t
A．Y
B．N
C．NG
第4题
High speed trains may be an answer. One fairly new proposal for such trains is for some- thing called a Maglev, meaning a magnetically levitated train. Maglev will not actually ride on the tracks, but will fly above tracks that are magnetically activated. This will save wear and tear on the tracks. These trains will be able to go faster than 150 miles per hour. At this speed, conventional trains have trouble staying on the tracks.
As you can see, Maglev offers exciting possibilities for the future.
What is the main topic of the talk？
A．Energy conversation.
B．Transportation of the future.
C．Transportation problem.
D．Advantages of air transportation over railroad.
第5题
Which Low Carbon Technology Is Now a Reality？
A．With fossil fuels expected to supply over 70% of the world"s energy needs by 2040， we face some urgent questions: where should efforts be focused in reducing greenhouse gas emissions？ Which technologies hold the most promise？ There are a range of low-carbon solutions and given the challenge， we will need them all．We hear a lot about the advances being made by refreshable sources of energy such as solar， wind and hydro-electricity and these are certainly valuable technologies in combating climate change．But how can we really make a m jor impact in reducing carbon emissions from large power plants and industrial facilities？ Enter carbon capture and storage——or CCS——a technology that captures CO2 from fossil fuel production and permanently stores it underground．
B．The aim is to prevent the release of large quantities of CO2 into the atmosphere （from fossil fuel use in power generation and other industries ）．It is a potential means of relieving the contribution of fossil fuel emissions to global warming and ocean acidification （酸化）．Although CO2 has been injected into geological formations for several decades for various purposes， including enhanced oil
recovery， the long term storage of CO2 is a relatively new concept．The first commercial example was Weyburn in 2000．CCS can also be used to describe the scrubbing （涤气 ） of CO2 from environmental air as a climate engineering technique．
C．In November 2014 the Global CCS Institute released its flagship （核心的） publication——the annual Global Status of CCS report．This comprehensive annual update is the prominent source of information on the development of CCS around the world．A lot of work went into updating information in the report， in cooperation with the CCS industry， as there had been quite significant changes to the CCS landscape in the preceding 12 months．This included the launch of a large-scale
CCS project in the power sector and the beginning of construction of the world"s first large-scale CCS project in the iron and steel sector．
D．Large-scale CCS is now a reality in the power sector with the October 2014 launch of the Boundary Dam Integrated Carbon Capture and Storage Demonstration Project in Saskatchewan， Canada．Boundary Dam is the first commercial CCS plant in the power sector， removing 90 per cent of the CO2 produced by electricity generation from lignite （褐煤） coal at Production Unit No．3 of the SaskPower facility．The captured CO is primarily used for enhanced oil recovery （EOR） at the nearby Weyburn oil field， although amounts are also to be stored in deep geological formations at the Aqnistore site．The success of the Boundary Dam project and the progression of additional
projects through planning and construction， indicates that CCS technologies for application in the power sector are "market ready"．
E．The next 18 -24 months will see CCS be applied across a range of industries and storage types．A further two large-scale CCS power projects are in construction in the US——the Kemper County Energy Facility in Mississippi and the Petra Nova Carbon Capture Project in Texas．Both projects are expected to be operational in 2016．Also in the US， the Illinois Industrial CCS project planned for launch later this year will capture CO2 from the Archer Daniels Midland corn-to-ethanol （乙醇） plant in Decatur， Illinois for storage in an onshore deep saline formation．The Abu Dhabi CCS project in the United Arab Emirates is under construction and from 2016 will provide the world"s first large- scale demonstration of CO2 capture from iron and steel production．
F．In addition to the 22 large-scale CCS projects currently in operation or construction around the world，14 projects are in advanced stages of planning， many of which are likely to be in a position to make a final investment decision over the coming year．Together this group of projects covers a range of applications for CCS and could extend to around ten in the number of large-scale CCS projects operating in the power sector by the end of the decade．Their progression to operation would add experience in the dedicated geological storage of CO．and see operational large-scale CCS activity extend to China for the first time．
G．2014 saw commercial application in the power sector become a reality and we can look forward to a further expansion across a diverse range of industries in the coming years．The Global CCS Institute continues to cover developments in CCS with up-to-date information， expert insights， workshops， media releases and online seminars．We struggle to make CCS industry information easily accessible and encourage you to engage with us via our website and regular publications．
H．For detailed information on large-scale CCS projects please visit our online Projects page， which you can browse or search for projects based on stage， region， industry o．r capture， transport and storage type．For the first time the Institute"s website contains project descriptions for around 40 lesser scale "remarkable" CCS projects， of which four Japanese "remarkable" CCS projects were the key focus of a chapter in the Global Status of CCS report．For ongoing expert information visit our Insights page， which is regularly updated with articles from experts in carbon capture and storage， public engagement， legal issues and policy developments．
I．To join in the discussion you can attend meetings and workshops around the world， and participate in online seminars where you will have the opportunity to listen to and ask questions of a range of experts．Visit our Events page to see upcoming meetings， conferences， workshops and seminars．Finally， for a range of up-to-date news and more detailed information， visit our news and publications sections．We look forward to covering this exciting period in the development of CCS and providing you with the latest information and important issues for the sector．
Carbon dioxide has been stored in geological formations for different purposes； however， its long term storage is comparatively new． 查看材料
第6题
Natural-gas Vehicles
Kermit the Frog once said, "It's not that easy bein' green." Although he wasn't referring to cars, his observation seems particularly appropriate for the auto industry today: Designing, developing and marketing "green" cars has not been an easy task, which is why gasoline-powered vehicles still rule the road and fossil fuels still account for almost 75 percent of the world' s energy consumption. As gasoline prices soar and concern over harmful emission mounts, how ever, cars that run on alternate fuel sources will become increasingly important. A natural-gas vehicle, or NGV, is the perfect example of such a car -- it's fuel-efficient, environmentally friendly and offers a relatively low cost of ownership.
Natural Gas Basics
The word "gas" is a confusing term because it is used to describe many different substances that are similar but not exactly the same. For example, tile "gas" you put in your car is gasoline, one component of crude oil, or petroleum. Petroleum is a dark, sticky liquid mixture of compounds formed underground by the decay of ancient marine animals.
Natural gas also comes from the decay of ancient organisms, but it naturally takes a gaseous form. instead of a liquid form. Natural gas commonly occurs in association with crude oil. It is derived from both land plants and aquatic organic matter and forms above or below oil deposits. It is often dissolved in crude oil at the high pressures existing in a reservoir. There are also reservoirs of natural gas, known as non-associated gas, that contain only gas and no oil.
Natural gas consists primarily of methane and other hydrocarbon gases. Hydrocarbons are organic compounds composed only of the elements carbon and hydrogen. The hydrocarbons in natural gas are called saturated hydrocarbons because they contain hydrogen and carbon bound together by single bonds.
Like gasoline, natural gas is combustible, which means it can be used in a combustion engine like gasoline. But cars that could burn natural gas didn't appear on the scene until the 1930s.
From Field to Ford
We extract natural gas trapped in underground reservoirs by drilling wells into the earth. A modern well, equipped with diamond-studded drill bits, can drill to depths approaching 25,000 feet.
Throughout the 19th century, the use of natural gas remained localized because there was no way to transport large quantities of gas over long distances. In 1890, the invention of a leak proof pipeline coupling made it possible to transport gas miles from the source. Improvements in pipeline technology continued over the next two decades until long-distance gas transmission became practical. From 1927 to 1931, laborers constructed more than 10 major natural gas transmission systems in the United States, making natural gas a viable energy source for many applications. The oil shortages of the late 1960s and early 1970s brought renewed interest in natural gas as a fuel source, especially for automobiles.
Today, owners of natural-gas vehicles can fill up their cars at one of 1,300 fueling stations located in the United States. Honda also offers a personal natural gas pump to people who purchase its natural-gas-powered Civic. The pump uses a home's existing natural gas lines and can be installed for $ 500 to $1500.
Natural-gas Vehicle Design
Natural-gas Vehicles use the same basic principles as gasoline-powered vehicles. In other words, the fuel(natural gas in this case)is mixed with air in the cylinder of a four-stroke engine and then ignited by a spark plug to move a piston up and down. Although there are some differences between natural gas and gasoline in terms of flammability and ignition temperatures, NGVs themselves operate on the same fundamental concepts as gasoline-powered vehicles.
Still, some modifications are required to make an NGV
A．Y
B．N
C．NG
第7题
Section B – TWO questions ONLY to be attempted
Louieed Co
Louieed Co, a listed company, is a major supplier of educational material, selling its products in many countries. It supplies schools and colleges and also produces learning material for business and professional exams. Louieed Co has exclusive contracts to produce material for some examining bodies. Louieed Co has a well-defined management structure with formal processes for making major decisions.
Although Louieed Co produces online learning material, most of its profits are still derived from sales of traditional textbooks. Louieed Co’s growth in profits over the last few years has been slow and its directors are currently reviewing its long-term strategy. One area in which they feel that Louieed Co must become much more involved is the production of online testing materials for exams and to validate course and textbook learning.
Bid for Tidded Co
Louieed Co has recently made a bid for Tidded Co, a smaller listed company. Tidded Co also supplies a range of educational material, but has been one of the leaders in the development of online testing and has shown strong profit growth over recent years. All of Tidded Co’s initial five founders remain on its board and still hold 45% of its issued share capital between them. From the start, Tidded Co’s directors have been used to making quick decisions in their areas of responsibility. Although listing has imposed some formalities, Tidded Co has remained focused on acting quickly to gain competitive advantage, with the five founders continuing to give strong leadership.
Louieed Co’s initial bid of five shares in Louieed Co for three shares in Tidded Co was rejected by Tidded Co’s board. There has been further discussion between the two boards since the initial offer was rejected and Louieed Co’s board is now considering a proposal to offer Tidded Co’s shareholders two shares in Louieed Co for one share in Tidded Co or a cash alternative of $22·75 per Tidded Co share. It is expected that Tidded Co&39;s shareholders will choose one of the following options:
(i) To accept the two-shares-for-one-share offer for all the Tidded Co shares; or,
(ii) To accept the cash offer for all the Tidded Co shares; or,
(iii) 60% of the shareholders will take up the two-shares-for-one-share offer and the remaining 40% will take the cash offer.
In case of the third option being accepted, it is thought that three of the company&39;s founders, holding 20% of the share capital in total, will take the cash offer and not join the combined company. The remaining two founders will probably continue to be involved in the business and be members of the combined company&39;s board.
Louieed Co’s finance director has estimated that the merger will produce annual post-tax synergies of $20 million. He expects Louieed Co’s current price-earnings (P/E) ratio to remain unchanged after the acquisition.
Extracts from the two companies’ most recent accounts are shown below:
The tax rate applicable to both companies is 20%.
Assume that Louieed Co can obtain further debt funding at a pre-tax cost of 7·5% and that the return on cash surpluses is 5% pre-tax.
Assume also that any debt funding needed to complete the acquisition will be reduced instantly by the balances of cash and cash equivalents held by Louieed Co and Tidded Co.
Required:
(a) Discuss the advantages and disadvantages of the acquisition of Tidded Co from the viewpoint of Louieed Co. (6 marks)
(b) Calculate the P/E ratios of Tidded Co implied by the terms of Louieed Co’s initial and proposed offers, for all three of the above options. (5 marks)
(c) Calculate, and comment on, the funding required for the acquisition of Tidded Co and the impact on Louieed Co’s earnings per share and gearing, for each of the three options given above.
Note: Up to 10 marks are available for the calculations. (14 marks)
第8题
The statement of financial position of BKB Co provides the following information:
BKB Co has an equity beta of 1·2 and the ex-dividend market value of the company’s equity is $125 million. The ex-interest market value of the convertible bonds is $21 million and the ex-dividend market value of the preference shares is $6·25 million.
The convertible bonds of BKB Co have a conversion ratio of 19 ordinary shares per bond. The conversion date and redemption date are both on the same date in five years’ time. The current ordinary share price of BKB Co is expected to increase by 4% per year for the foreseeable future.
The overdraft has a variable interest rate which is currently 6% per year and BKB Co expects this to increase in the near future. The overdraft has not changed in size over the last financial year, although one year ago the overdraft interest rate was 4% per year. The company’s bank will not allow the overdraft to increase from its current level.
The equity risk premium is 5% per year and the risk-free rate of return is 4% per year. BKB Co pays profit tax at an annual rate of 30% per year.
Required:
(a) Calculate the market value after-tax weighted average cost of capital of BKB Co, explaining clearly any assumptions you make. (12 marks)
(b) Discuss why market value weighted average cost of capital is preferred to book value weighted average cost of capital when making investment decisions. (4 marks)
(c) Comment on the interest rate risk faced by BKB Co and discuss briefly how this risk can be managed. (5 marks)
(d) Discuss the attractions to a company of convertible debt compared to a bank loan of a similar maturity as a source of finance. (4 marks)
第9题
Rocket Renaissance
The Ear of Private Spaceflight Is About to Start
Background
Two years ago, people witnessed the first space travel by SpaceShip One. Three people were involved in this flight: Burt Rutan, who designed the craft, and Mike Melvill, who flew it--although they were ably assisted by Paul Allen, one of the founders of Microsoft, who paid for it. Certainly, people have long been known that manned spaceflight was possible. What they showed was that it is not just a game for governments. Private individuals can play, too.
People involved
Now, lots of people want to join in, and most of them have just met up at the International Space Development Conference in Los Angeles, to engage in that mixture of camaraderie and competition that characterises the beginnings of a new technology. And, as might be expected, they have two of the necessary ingredients of success: ideas and money.
First, the money. So far, more than $1 billion is known to have been committed to building private spaceships and the infrastructure to support them. For example, Mr.. Rum&39; s follow-up vehicle, SpaceShip Two, is expected to cost its backers, Virgin Galactic, $240m for a fleet of five. The spaceport in New Mexico from which these are intended to fly will account for another $225m, although New Mexico&39;s government is planning to raise this money itself.
These are not small sums, of course. On the other hand, Virgin Galactic has already banked $14m of deposits towards the $200,000 fare from people who want to travel on SpaceShip Two, even though it has yet to be built, let alone flown.
All this suggests that spaceflight, if not exactly entering the age of the common man, is at least entering the age of the moderately prosperous enthusiast. For entrepreneurs, it is no longer necessary to have billions of dollars to get into space; millions will now do. And for those who merely wish to travel there, and have enough money in their bank account, reality is favourable.
Get started
As with aircraft a century ago, a lot of designs are competing with each other, and there is no certainty about which will succeed. The initial goal is to build a "suborbital" vehicle. This will not have to develop the tremendous speed needed to go into orbit around the Earth. instead, it will travel briefly into space, offering a short thrilling ride out of the atmosphere, a few minutes of weightlessness, and a spectacular view of the planet from about 100kin. Four important criteria are how you take off, what fuel you use, what your craft is made of, and how you come back.
Most people&39;s vision of a rocket launch is straight up from the ground. But, of the five vehicles most likely to be developed, two will actually be launched from the air. SpaceShip Two will be carded to high altitude by a purpose-built aircraft known as Eve before its rocket motor is ignited. And Explorer, a vehicle being designed by Space Adventures, will be launched from the top of a high-altitude Russian research plane called the M-55X, according to Eric Anderson, the firm&39;s president and chief executive.
As Dennis Jenkins, a consultant engineer at NASA, America&39;s space agency, points out, this is similar to using a two-stage rocket to get into space, with the aircraft acting as the first stage. However, a plane offers several advantages over a throw-away booster rocket. First, it can be used again. Second, it uses oxygen from the air, rather than having to carry its own oxidant, which saves weight. Third, it is lifted by wings. That means the atmosphere is an advantage, rather than a hindrance. All this means that the spacecraft itself can be lighter and cheaper.
Not everyone wants to run two vehicles, though. Jeff Greason, president of XCOR Aerospace, a firm based in Mojave, California, is developing a two-person, ground-launched suborbital rocketplane called Xerus. Launching from the ground, says Mr. Greason, is more difficult than air launching, but he reckons that in this case it has significantly lower operating costs.
Fuel choices
The second important design choice is the type of fuel. Unlike a jet engine, a rocket carries its own oxidant (氧第剂). This is why it can operate in space. Sometimes that oxidant is oxygen itself, in liquid form. In that case the fuel, too, is usually liquid-either kerosene (煤油) or liquid hydrogen (氢) —and the two liquids are stored in separate tanks until they meet in the rocket&39;s combustion chamber. Alternatively, both fuel and oxidant are solid, and are loaded pre-mixed, like the propellant of a firework rocket.
SpaceShip Two, though, follows the design of SpaceShip One and is powered by a mixture of the two. The combustion chamber of a mixture is partly filled with solid fuel but no oxidant. However, the fuel is coated round the inside of the chamber, leaving a hole through the middle into which a liquid or gaseous oxidant can be pumped, and out of which the exhaust emerges. In SpaceShip One, the fuel was rubber and the oxidant a liquefied gas called nitrous oxide (一氧化二氮).
Proponents of mixture say they are safer than either pure solid or pure liquid rockets. George Whittinghill, Virgin Galactic&39;s chief technologist, says that they are safer than solid rockets because the flow of oxidant can be controlled, and combustion halted, if there is a problem. Solid rockets, like the fireworks they resemble, cannot be stopped until they run out of fuel. On the other hand liquid-fuelled engines, though they can be shut down, are complex and temperamental. As Mr. Whittinghill observes, "they have pumps, seals, valves and lines everywhere, and there is a lot that potentially could go wrong."
All this rather irrates those working on liquid propulsion. Richard Pournelle, head of investor relations at XCOR Aerospace, says the comparison is unfair. Liquid propulsion is routine in rocketry while hybrids are still rare. Numbers alone, therefore, mean that liquid-fuelled rockets blow up more often. That, Mr. Pournelle argues, does not prove that they are inherently unsafe. Chuck Lauer, vice- president of business development for Rocketplane, another firm going down the liquid-fuelled route, agrees and argues that kerosene is widely used as aviation fuel and nobody complains that it is unsafe.
1. It is only two years ago that people became aware of the fact that manned spaceflight was actually possible.
A.Y
B.N
C.NG
Spaceflight is possible for individuals who want to fly in the space and who have the money.
A.Y
B.N
C.NG
The initial goal of building an aircraft is to make the vehicle fly, and speed was not such a primary consideration.
A.Y
B.N
C.NG
All of the five vehicles most likely to be developed will be launched from the air.
A.Y
B.N
C.NG
Although it is possible to launch the spaceship both from ground and from the air, some people believe it&39;s more cost-effective to launch it from ground.
A.Y
B.N
C.NG
A consultant engineer at NASA points out that using aircraft acting as the first Stage provides several advantages over a throw-away booster rocket.
A.Y
B.N
C.NG
In the design considerations of a spaceship, fuel choice is as important as the method of launching.
A.Y
B.N
C.NG
A rocket carries its own oxidant, and its fuel is usually either kerosene or______.
Proponents of mixture say that they are______than either pure solid or pure liquid rockets.
Proponents of kerosene cite the example of______using it as fuel
请帮忙给出每个问题的正确答案和分析，谢谢！
第10题
Automobiles VS Public Transport
Public transport plays a central role in any efficient urban transport system in developing countries, where at least 16 cities are expected to have more than 12 million people each by the end of this decade, failing to give priority to public transport would be disastrous.
The term "public transport" covers many different types of vehicles, but most commonly refers to buses and trains. Rail services fall into four major categories: rapid rail (also called the underground, tube, metro, or subway), which operates on exclusive rights-of-way (优先行驶权) in tunnels or on elevated tracks; trams, which move with other traffic on regular streets; light rail, which is a quieter, more modern version of trams that can run either on exclusive rights-of-way or with other traffic: and suburban or regional trains, which connect a city with surrounding areas.
The recent trend in many cities is toward light rail over "heavy" rapid-rail systems. Whereas metros require exclusive rights-of-way, which often means building costly elevated or underground lines and stations, light rail can be built on regular city streets.
The concept of public transport also includes organized car pools, in which several people share the cost of riding together in the same private automobile. For US commuters in areas with inadequate bus and train services, this is the only "public" transport option. But even where other systems are comprehensive, there is vast potential for car pooling; recent research shows that in cities the world over, private cars during commuting hours on average carry just 1.2 1.3 persons per vehicle.
Public transport modes vary in fuel use and emissions and in the space they require, but if carrying reasonable numbers of passengers, they all perform. better than single-occupant private cars on each of these counts.
Although energy requirements vary according to the size and design of the vehicle and how many people are on board, buses and trains require far less fuel per passenger for each kilometer of travel. In the United States, for example, a light-rail vehicle needs an estimated 640 BTUs (British Thermal Units, measure of energy consumed) of energy per passenger per kilometer; a city bus would use some 690 BTUs per passenger-kilometer; and a car pool with four occupants 1,140 BTUs. A single-occupant automobile, by contrast, consumes nearly 4,580 BTUs per passenger-kilometer.
The pollution savings from public transport are even more dramatic. Since both rapid and light rail have electric engines, pollution is measured not from the motor exhaust, but from the power plant generating electricity, which is usually located outside the city, where air quality problems are less serious. For typical U.S. commuter routes, rapid rail emits 30 grams of nitrogen oxides for every 100 kilometers each rail passenger travels, compared with 43 grams for light rail, 95 grams for transit buses, and 128 grams for single-occupant automobiles. Public transport's potential for reducing hydrocarbon (碳氢化合物)and carbon monoxide(一氧化碳)emissions is even greater.
Although diesel buses—especially in developing countries—can be heavy polluters, existing technologies, such as filters, can control their exhaust. Buses can also run on less polluting fuels such as propane (丙烷, used in parts of Europe) and natural gas (used in Brazil and China). Test buses in the Netherlands that run on natural gas are estimated to emit 90 percent less nitrogen oxide and 25 percent less carbon monoxide than diesel engines do.
In addition to reducing fuel consumption and pollution, public transport saves valuable city space. Buses and trains carry more people in each vehicle and, if they operate on their own rights-of-way, can safely run at much higher speeds. In other words, they not only take up less space but also occupy it for
A．Y
B．N
C．NG
