城市轨道交通专业英语

城市轨道交通运营管理专业专业英语

朱海燕何静

上海工程技术大学

城市轨道交通学院

2009 年1 月

List

List

Chapter 1: Development of Urban Rail Transit Speeds up in China (3)

Chapter 2 Rapid Transit (12)

Chapter 3RAIL TRANSIT IN NORTH AMERICA (23)

Chapter 4 The Railroad Track (40)

Chapter 5 General Vehicle Description (45)

Chapter 6A TP Transmission and Moving Block (53)

Chapter 7Control of Railway Operation (62)

Chapter 8Train Station Passenger Flow Study (74)

Chapter 9Metrocard Fare Incentives (81)

Chapter 10 Audible Information Design in the New York City Subway (86)

Chapter 1: Development of Urban Rail Transit Speeds up in China With the development of urban rail transit, on the one hand, it is promoting the process of urban modernization, alleviating congested traffic in cities, and narrowing the distance between time and space. On the other hand, it changes the way people travel, accelerates the pace of their life and work, and affects the quality of life.

The state of urban rail transit reflects a country's comprehensive strength and is a symbol of a city's modernization level. At present, rail transit system is available in 135 cities in nearly 40 countries and regions. In cosmopolitan cities, accounting for a proportion of 60 per cent - 80 per cent, rail transit has become the leading means of transportation in these cities. Yet so far, in Beijing, Shanghai, Tianjin and Guangzhou, etc., rail transit accounts for less than 10 percent in the cities total traffic capacity.

Urban rail transit offers comprehensive advantages, like small land occupation, large traffic volume, high speed, non-pollution, low energy consumption, high safety and great comfort. With most facilities being installed underground and the operation going on underground, subways require very limited occupation of land, and do not compete with other means of transportation for space. Urban light rail, trolley bus as well as suburban rail and magnetic suspension train are basically railways, which makes it possible to make the most of land resources.

Urban rail transit system offers immense transport capacity. During rush hours, the maximum unidirectional transport capacity may reach up to 60, 000- 80, 000 person-times per hour, which is unmatchable to other means of transportation. The hourly traveling speed of rail transit generally exceeds 70 kilometers-100 kilometers, offering high punctuality. Moreover, mostly being hauled by electric locomotives, rail transit requires low energy consumption, and it causes little pollution to cities. Therefore, it is called "green transportation".

From a macro perspective, urban rail transit plays an important role in improving the structure of urban transport, alleviating urban ground traffic congestion, and promoting the utilization efficiency of urban land.

Nevertheless, compared with other means of transportation, rail transit has some drawbacks, like long construction cycle, heavy initial investment, slow withdrawal of funds and poor economic benefits in operation. For example, currently the building of subway costs some RMB500 million-700 million per kilometer; urban light rail and magnetic suspension train, RMB200 million-300 million; trolley bus and suburban rail, about RMB100 million.

In China, rail transit dates back to the late 1960s, when the first subway was built in

Beijing. That was nearly one century later than developed countries in the West. However, since it made its debut, urban rail transit has helped ease the immense pressure caused by urban traffic congestion and brought great convenience and comfort to passengers. Take Beijing for example. Currently, subways provide a transport volume of approximately 1.5 million person-times per day. Without subways, the traffic congestion in this city would simply be inconceivable.

At present, rail transit has evolved from the startup stage to a period of stable, sustainable and orderly development in this country. In China (excluding Hong Kong and Taiwan), the length of subways completed totals 193 kilometers; project urban rail under construction, 334 kilometers; planned urban rail, 420 kilometers. Among big cities with a population of over 2 million, those that already have or are building urban rail transit include Beijing, Tianjin, Shanghai, Guangzhou, Dalian, Shenzhen, Wuhan, Nanjing, Chongqing and Changchun. Now, seven cities have announced or are still working on their plan to build rail transit: Chengdu, Hangzhou, Shenyang, Xi'an, Harbin, Qingdao and Suzhou.

According to plan, by 2008, there will be thirteen rail transit lines and two spur lines in Beijing, with a total length of 408.2 kilometers. In Shanghai, there will be 21 rail transit lines, totaling more than 500 kilometers in length. During the Tenth Five-Year Plan period, the total length will hit 780 kilometers. In Tianjin, there will be four subway lines, totaling 106 kilometers. That, coupled with 50 kilometers of suburban light rail and one loop subway 71-kilometers set aside, will bring the total length to 227 kilometers. Meanwhile, there will be seven rail transit lines totaling 206.48 kilometers in Guangzhou, and seven rail transit lines totaling 263.1 kilometers in Nanjing. With other cities' planning taken into account, the total length of rail transit lines will come to some 2, 200 kilometers in this country.

At present, the constraints to the development of rail transit in China mainly lie in three aspects:

First, there is severe shortage of construction funds. According to the foregoing planning, it is necessary to invest in approximately RMB300 billion. Projects to be completed by 2006 alone require more than RMB150 billion. Furthermore, in most cases, funds come from investments of the central and local governments as well as bank loans. Still a developing country as it is, China has very limited financial strength.

Second, as rail transit is demanding on technical standard, some key technical facilities at low ratio of home mading at present largely rely on imports. Thus, construction cost remains hig h due to the import of large quantity of technolog y and equipment.

Third, in most cases, rail transit operates at a loss in China. That aggregates the central

and local governments' financial burdens, which, in return, checks the development of rail transit to some extent.

For this reason, China formulated the guideline of "doing what the strength allows, implementing rules-based management and pursuing stable development". In the development of rail transit, it is required that homemade equipment should take up at least 70 per cent. Meanwhile, it is essential to ensure that development of rail transit suits the pace of economic development in the cities and prevent blind development and irrational attempts to advance forward.

Railway Terms and New Words

urban adj. 城市的, 市内的, urban rail transit（URT）城市轨道交通alleviate vt. 减轻

congested adj. 拥挤的，congest vt.，congestion n.

accelerate v. 加速, 促进

comprehensive adj. 全面的，广泛的

cosmopolitan adj. 世界性的，全球（各地）的

proportion n. 比例, 均衡, 面积, 部分

underground adj. 地下的, 地面下的, 秘密的n. [英] 地铁adv. 秘密地trolley bus n. 电车, (电车)滚轮, 手推车, 手摇车, 台车

magnetic adj. 磁的, 有磁性的, 有吸引力的

suspension n. 吊, 悬浮, 悬浮液, 暂停, 中止, 悬而未决, 延迟

basically adv. 基本上, 主要地

unidirectional adj. 单向的, 单向性的

the Tenth Five-Year Plan 第十个五年规划

at a loss 低于成本的

in return 作为报答

compete with 与…争夺，competition n.

Reading Material

The Rising Motorization of China

China’s motorization rate has grown in accordance with other rapidly developing countries, but because of China’s high population, the impacts of motorization are potentially more severe. Figure 1 shows the exponential increase in personal automobile ownership rates. Currently, there are about seven personal automobiles per 1000 people,

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compared to over 700 vehicles per 1000 people in industrialized nations like the United States. This figure does not include privately owned trucks or publicly owned vehicles (including buses and trucks), which increases the number of automobiles to about 28 vehicles per 1000 people. If China were to achieve motorization rates comparable to those of developed countries, the environmental and economic consequences could be disastrous. By 2020, the total automobile fleet (not including motorcycles) is expected to grow by between three and seven times the current size depending on economic growth rates (NRC 2003).

The population distribution of China is diverse, with the majority of the population (60%) living in rural areas. However, in the past several decades, the improved economic situation of the cities has caused a rapid urban in-migration. This trend has resulted in a nearly three-fold increase in urban development and density in the last decade as displayed in Figure 2. Much of this development is not necessarily representative of sustainable transit and pedestrian oriented growth. Although this new development is very dense, low land cost at the periphery cause developers to build spatially separated housing and commercial developments with few transit connections to the urban center (Gaukenheimer 1996).

The western provinces are the most sparsely populated with the largest urban population centers located in provinces along the eastern coast, in metropolises such as Shanghai, Beijing, and Guangzhou. These cities have been experiencing high motorization rates partially because of their higher incomes, but non-motorized modes still capture approximately 70% of the work trip commutes in these cities, while the personal automobile only accounts for 7% (Hu 2003). Much of the transportation and planning research has been centered on these cities, although they constitute a rather small portion of the entire population. Figure 3 shows the amount of cities of different sizes and the approximate total population of people living in cities of different size. Two thirds of the urban population resides in cities with populations between 0.5 and 2 million, indicating that much of the planning and transportation research related to China is focusing on problems that might not be relevant or applicable to the majority of the Chinese population. Economically, most of these cities are years or decades behind the more developed Chinese cities and have not developed many of the transportation problems Beijing, Shanghai and Guangzhou have. Focusing planning efforts in these cities could have much greater returns.

The Chinese economy has been growing at a phenomenal rate for the past decade and has doubled in size in the last nine years. In fact, the growth rate is so fast that the Chinese government is imposing several measures to try to control growth to keep it at a more sustainable level (Economist 2004). China’s growth has largely been a result of investment in a few “pilla r” industries. The highest growing pillar industries are: electronic manufacturing, automobiles, electric power, and steel. The eighth five-year plan (1991-1995) designated the automobile industry as one of the pillar industries of economic development. This policy statement encourages the growth of an indigenous auto industry that will be able to supply a large portion of its domestic demand and create a strong export market. It calls for the consolidation of over one hundred companies into 3 or 4 large

competitive companies. The auto industry accounts for 20% of Shanghai’s gross regional product (Hook 2002). However, with China’s entry into the World Trade Organization (WTO) in 2001, they must reduce tariffs on imported automobiles and can no longer protect their market. This has spurred development of the domestic automobile industry to a level that can compete with international competitors. One of the greatest challenges of cities in China is controlling automobile ownership growth, while fostering the national policy of growing the automobile industry.

Costs and Benefits of Motorization

The cost and benefit implications for Chinese motorization are enormous. Motorization is a major economic growth strategy. The government has adopted a strategy of developing an automobile manufacturing industry. Automobiles can also provide indirect economic benefits of decreased travel time, improved accessibility to goods and services, and new found mobility that will cause people to travel more and achieve a more mobile lifestyle that they would not have otherwise been able to experience.

The potential costs are enormous. The United States has the highest motorization rate in the world and perhaps the most mature automobile industry. However, the US has also experienced very high costs associated with our level of motorization. The most obvious and potentially most severe cost is the air pollution and greenhouse gas emissions associated with the automobile. The US emits 26% of the global greenhouse gases but only constitutes 5% of the worl d’s population. China’s policy goal is to achieve Euro II emissions standards by 2005 (about a decade behind Europe) and be internationally compliant with Euro IV standards by 2010. This is a very ambitious goal, but it is necessary if Chinese automakers want to compete in the international market and improve the air quality in their own country. With the three to seven-fold growth rate anticipated in the next 15 years, CO2 emissions will likely quadruple, CO, and hydrocarbons will likely triple, and NO x and particulate matter will likely stay the same. This assumes an aggressive emissions regulation strategy and a modest economic growth rate (NRC 2003). The US EPA has identified all of these emissions as having serious health effects at high concentrations. From a global perspective, China’s motorization could have adverse effects on the global climate. Currently, the transportation sector accounts for 17% of the greenhouse emissions, but this proportion could increase significantly if the motorization trends continue. China is also the second highest consumer of oil in the world (behind the United States). If China motorizes as rapidly as expected, the increase demand could cause the global price of fuel to skyrocket.

Another major issue associated with increased motorization is changes in land use. As incomes increase, people desire more living space, which reduces density and encourages expansion at the urban fringe. Figure 4 shows the growth of residential floor space per capita, which is a force toward lower density. This requires more auto oriented transportation infrastructure as well as more land for development. In Shanghai, approximately 10% of the land area is devoted to transportation infrastructure (compared to 20-25% in Europe) (Shen 1997). Because of the built environment, most of the new transportation infrastructure is expanding at the periphery, encouraging auto oriented developments. An increasingly open housing market, where people choose where to live is also creating a spatial jobs-housing imbalance that did not previously exist, when industry provided housing for its employees adjacent to their plants. This greatly increases the cost of transportation for Chinese households as indicated by Figure 5. The proportion of a households income spent on transportation has increases ten fold in less than 15 years. Another major consideration is the conservation of agricultural land. China currently has a very low amount of agricultural land per capita (World Bank 2001)and cannot afford to lose more through urban expansion (Franke 1997).

Additional costs include accidents and injuries associated with motorization. Currently, the fatality rate (deaths per mile of travel) is 30 times that of the United States, with over 100,000 deaths per year since 2001, many of which are pedestrians and bicyclists (NRC 2003, Hook 2002b). Additionally equity issues must be considered, specifically the dislocation of the poor. Even with the high projected growth rates in automobile ownership, most Chinese will not own vehicles, so alternative modes must be supplied that can serve the increasing spatial separation between origins and destinations. The cost of the required infrastructure will be enormous and the government will likely have to provide more subsidies to the transportation sector, potentially restricting its investment in other sectors.

Causes of Motorization

The primary impetus for the motorization of China has been the rapid growth of the economy. With a rise in the economic growth of a country comes a desire and means to become more motorized. Motorization rates are associated with a country’s gross domestic product (GDP). Countries with low GDP (below $800) generally have a high proportion of trucks and buses in their vehicle fleets. As GDP increases up to about $10,000, the share of personal automobiles increases drastically until a saturation level is reached (NRC 2003). China’s GDP has been increasing by more than 8% annually for over a decade. A large proportion of upper income people can now afford the luxury of the automobile.

Kenworthy et. al. (1999) argue that, while GDP plays an important role, there are many other factors that likely influence motorization rates. By comparing cities with similar GDP and very different transportation energy use, they conclude that land use is a primary factor influencing energy use and thus motorization. Additionally demand management schemes can limit the adverse effect of motorization in China. Currently China’s regulatory structure is weak and inconsistent. Some cities have effectively provided competitive transit alternatives and limited outward expansion (Joos 2000). Others have fully embraced the automobile, pushing many other modes to the side.

Railway Terms and New Words

motorization n.动力化, 摩托化

exponential diverse migration metropolis adj.

adj.

n.

n.

指数的, 幂数的

不同的, 变化多的

移民, 移植, 移往, 移动

大城市Chicago, the metropolis of the Midwest.

skyrocket v.暴涨，猛涨迅速和突然地升高或使升高：fringe n.边缘, 须边, 刘海

periphery n.外围

fatality n.命运决定的事物, 不幸, 灾祸, 天命dislocation n.混乱, 断层, 脱臼

saturation n.饱和(状态), 浸润, 浸透，饱和度

in accordance with 与...一致, 依照

per capita 按人口平均计算

Chapter 2 Rapid Transit

A rapid transit, underground, subway, elevated, or metro system is a railway system, generally in an urban area, that generally has high capacity and frequency, with large trains and total or near total grade separation from other traffic.

Definitions and Nomenclature

There is no single term in English that all speakers would use for all rapid transit or metro systems. This fact reflects variations not only in national and regional usage, but in what characteristics are considered essential.

One definition of a metro system is as follows; an urban, electric mass transit railway system totally independent from other traffic with high service frequency.

But those who prefer the American term "subway" or the British "underground" would additionally specify that the tracks and stations must be located below street level so that pedestrians and road users see the street exactly as it would be without the subway; or at least that this must be true for the most important, central parts of the system. On the contrary, those who prefer the American "rapid transit" or the newer term "metro" tend to regard this as a less important characteristic and are pleased to include systems that are completely elevated or at ground level ( at grade) as long as the other criteria are met. A rapid transit system that is generally above street level may be called an "elevated" system (often shortened to el or, in Chicago, "L" ). In some cities the word "subway" applies to the entire system, in others only to those parts that actually are underground; and analogously for "el".

Germanic languages usually use names meaning "underground railway" (such as "subway" or "U-Bahn"), while many others use "metro".

Train Size and Motive Power

Some urban rail lines are built to the full size of main-line railways; others use smaller tunnels, limiting the size and sometimes the shape of the trains (in the London Underground the informal term tube train is commonly used). Some lines use light rail rolling stock, perhaps surface cars merely routed into a tunnel for all or part of their route. In many cities, such as London and Boston's MB-TA, lines using different types of vehicles are organized into a single unified system.

Although the initial lines of what became the London Underground used steam engines, most metro trains, both now and historically, are electric multiple units, with steel wheels running on two steel rails. Power is usually supplied by means of a single live third rail (as in New York) at 600 to 750 volts, but some systems use two live rails (noticeably London) and thus eliminate the return current from the running rails. Overhead wires, allowing

higher voltages, are more likely to be used on metro systems without much length in tunnel, as in Amsterdam; but they also exist on some that are underground, as in Madrid. Boston's Green Line trains derive power from an overhead wire, both while traveling in a tunnel in the central city and at street level in the suburban areas.

Systems usually use DC power instead of AC, even if this requires large rectifiers for the power supply. DC motors were formerly more efficient for railway applications, and once a DC system is in place, converting it to AC is usually considered too large a project to contemplate.

Tracks

Most rapid transit systems use conventional railway tracks, though since tracks in subway tunnels are not exposed to wet weather, they are often fixed to the floor instead of resting on ballast. The rapid transit system in San Diego, California operates tracks on former railroad rights of way that were acquired by the governing entity.

Another technology using rubber tires on narrow concrete or steel railways was pioneered on the Paris M6tro, and the first complete system to use it was in Montreal. Additional horizontal wheels are required for guidance, and a conventional track is often provided in case of flat tires and for switching. Advocates of this system note that it is much quieter than conventional steel-wheeled trains, and allows for greater inclines given the increased traction allowed by the rubber tires.

Some cities with steep hills incorporate mountain railway technologies into their metros. The Lyon Metro includes a section of rack (cog) railway, while the Carmelit in Haifa is an underground funicular.

For elevated lines, still another alternative is the monorail. Supported or "straddle" monorails, with a single rail below the train, include the Tokyo Monorail; the Schwebebahn in Wuppertal is a suspended monorail, where the train body hangs below the wheels and rail. Monorails have never gained wide acceptance except for Japan, although Seattle has a short one, which it hopes to replace with a new, larger system, and one has lately been built in Las Vegas. One of the first monorail systems in the United States was installed at Anaheim's Disneyland in 1959 and connects the amusement park to a nearby hotel. Disneyland's builder, animator and filmmaker Walt Disney, offered to build a similar system between Anaheim and Los Angeles.

Crew Size and Automation

Early underground trains often carried an attendant on each car to operate the doors or gales, in addition to a driver. The introduction of powered doors around 1920 permitted crew sizes to be decreased, and trains in many cities are now operated by a single person. Where the operator would not be able to see the whole side of the train to tell whether the

doors can be safely closed, mirrors or closed-circuit TV monitors are often provided for that purpose.

An alternative to human drivers became available in the 1960s, as automated systems were developed that could start a train, accelerate to the correct speed, and stop automatically at the next station, also taking into account the information that a human driver would obtain from lineside or cab signals. The first complete line to use this technology was London's Victoria Line, in 1968. In usual operation the one crew member sits in the driver's position at the front, but just closes the doors at each station; the train then starts automatically. This style of system has become widespread. A variant is seen on London's Docklands Light Railway, opened in 1987, where the "passenger service agent" (formerly "train captain") rides with the passengers instead of sitting at the front as a driver would. The same technology would have allowed trains to operate completely automatically with no crew, just as most elevators do; and as the cost of automation has decreased, this has become financially attractive. But a countervailing argument is that of possible emergency situations. A crew member on board the train may be able to prevent the emergency in the first place, drive a partly failed train to the next station, assist with an evacuation if needed, or call for the correct emergency services (police, fire, or ambulance) and help direct them.

In some cities the same reasons are considered to justify a crew of two instead of one; one person drives from the front of the train, while the other operates the doors from a position farther back, and is more conveniently able to help passengers in the rear cars. The crew members may exchange roles on the reverse trip ( as in Toronto) or not (as in New York ) .

Completely crewless trains are more accepted on newer systems where there are no existing crews to be removed, and especially on light rail lines. Thus the first such system was the VAL (automated light vehicle) of Lille, France, inaugurated in 1983. Additional VAL lines have been built in other cities. In Canada, the Vancouver Sky Train carries no crew members, while Toronto's Scarborough RT, opening the same year (1985) with otherwise similar trains, uses human operators.

These systems generally use platform-edge doors (PEDs) , in order to improve safety and ensure passenger confidence, but this is not universal; for example, the Vancouver SkyTrain does not ( And on the contrary, some lines which retain drivers, however, still use PEDs, noticeably London' s Jubilee Line Extension. MTR of Hong Kong also uses platform screen doors, the first to install PSDs on an already operating system. ) With regard to larger trains, the Paris Metro has human drivers on most lines, but runs crewless trains on its newest line, Line 14, which opened in 1998. Singapore's North East

MRT Line (2003) claims to be the world' s first completely automated underground urban heavy rail line. The Disneyland Resort Line of Hong Kong MTR is also automated.

Tunnel Construction

The construction of an underground metro is an expensive project, often carried out over many years. There are several different methods of building underground lines.

In one usual method, known as cut-and-cover, the city streets are excavated and a tunnel structure strong enough to support the road above is built at the trench, which is then filled in and the roadway rebuilt. This method often involves extensive relocation of the utilities usually buried not for below city streets—especially power and telephone wiring, water and gas mains, and sewers. The structures are generally made of concrete, perhaps with structural columns of steel; in the oldest systems, brick and cast iron were used. Cut-and-cover construction can take so long that it is often necessary to build a temporary roadbed while construction is going on underneath in order to avoid closing main streets for long periods of time; in Toronto, a temporary surface on Yonge Street supported cars and streetcar tracks for several years while the Yonge subway was built.

Some American cities, like Newark, Cincinnati and Rochester, were originally built around canals. When the railways took the place of canals, they were able to bury a subway in the disused canal's trench, without rerouting other utilities, or acquiring a right of way piecemeal.

Another common way is to start with a vertical shaft and then dig the tunnels horizontally from there, often with a tunneling shield, thus avoiding almost any disturbance to existing streets, buildings, and utilities. But problems with ground water are more likely, and tunneling through native bedrock may require blasting. (The first city to extensively use deep tunneling was London, where a thick sedimentary layer of clay largely avoids both problems. ) The confined space in the tunnel also restricts the machinery that can be used, but specialised tunnel-boring machines are now available to overcome this challenge. One disadvantage with this, nevertheless, is that the cost of tunneling is much higher than building systems cut-and-cover, at-grade or elevated. Early tunnelling machines could not make tunnels large enough for conventional railway equipment, necessitating special low round trains, such as are still used by most of the London Underground, which cannot fix air conditioning on most of its lines because the amount of empty space between the trains and tunnel walls is so small.

The deepest metro system in the world was built in St. Petersburg, Russia. In this city, built ii the marshland, stable soil starts more than 50 meter deep. Above that level the soil is mostly made up of water-bearing finely dispersed sand. As a result of this, only three stations out of nearly 60 are built near the ground level and three more above the ground.

Some stations and tunnels lie as deep as 100-120 meters below the surface.

One advantage of deep tunnels is that they can dip in a basin-like profile between stations, without incurring significant extra costs owing to having to dig deeper. This technique, also referred to as putting stations "on humps" , allows gravity to help the trains as they accelerate from one station and brake at the next. It was used as early as 1890 on parts of the City and South London Railway, and has been used many times since.

Railway Terms and New Words

nomenclature n.命名法, 术语

analogous adj.类似的, 相似的, 可比拟的

rolling stock n.全部车辆

traction n.牵引

countervail v.补偿, 抵销

evacuate v.疏散,

inaugurate vt.举行就职典礼, 创新, 开辟, 举行开幕(落成、成立)典礼. excavated v.挖掘, 开凿, 挖出, 挖空

Reading Material

Light Rail

Light rail or light rail transit (LRT) is a particular class of urban and suburban passenger railway that uses equipment and infrastructure that is generally less massive than that used for rapid transit systems, with modern light rail vehicles usually running along the system.

Light rail is the successor term to streetcar, trolley and tram in many locales, although the term is most consistently applied to modern tram or trolley operations employing features more generally associated with metro or subway operations, including exclusive rights-of-way, multiple unit train configuration and signal control of operations.

The term light rail is derived from the British English term light railway long used to distinguish tram operations from steam railway lines, and also from its usually lighter infrastructure.

Light rail systems are almost universally operated by electricity delivered through overhead lines, though several systems are powered through different means, such as the JFK Airtrain, which uses a standard third rail for its electrical power, and trams in Bordeaux

which use a special third-rail configuration in which the rail is only powered while a tram is on top of it. A few unusual systems like the River Line in New Jersey and the 0-Train in Ottawa use diesel-powered trains, though this is sometimes intended as an interim measure until the funds to install electric power become available.

Definition

Most rail technologies, including high-speed, freight, commuter/regional, and metro/subway are considered to be "heavy rail" in comparison. A few systems such as people movers and personal rapid transit could be considered as even "lighter", at least in terms of how many passengers are moved per vehicle and the speed at which they travel. Monorails are also considered to be a separate technology. Light rail systems can handle steeper inclines than heavy rail, and curves sharp enough to fit within street intersections. They are generally built in urban areas, providing frequent service with small, light trains or single cars.

The most difficult distinction to draw is that between light rail and streetcar or tram systems. There is a significant amount of overlap between the technologies, and it is usual to classify streetcars/trams as a subtype of light rail instead of as a distinct type of transportation. The two common versions are:

1. The traditional type, where the tracks and trains run along the streets and share space with road traffic. Stops tend to be very frequent, but little effort is made to set up special stations. Because space is shared, the tracks are not usually visible.

2. A more modern variation, where the trains tend to run along their own right-of-way and are of-ten separated from road traffic. Stops are usually less frequent, and the vehicles are often got on from a platform. Tracks are highly visible, and in some cases significant effort is used to keep traffic away through the use of special signaling and even grade crossings with gate arms. At the highest degree of separation, it can be difficult to draw the line between light rail and metros, as in the case of London's Docklands Light Railway, which would likely not be considered "light" compared with London Underground.

Many light rail systems have a combination of the two, with both on road and off road sections. In some countries, only the latter is described as light rail. In those places, trams running on mixed right of way are not regarded as light rail, but considered distinctly as streetcars or trams.

Light rail is usually powered by electricity, generally by means of overhead wires, but sometimes by a live rail, also called third rail (a high voltage bar alongside the track) , requiring safety measures and warnings to the public not to touch it. In some cases, especially when initial funds are limited, diesel-powered versions have been used, but it is not a preferred option. Some systems, such as the JFK Airtrain in New York City, are

automatic without a driver; however, such systems are not what is usually thought of as light rail. Automatic operation is more common in smaller people mover systems than in light rail systems, where the possibility of grade crossings and street running make driverless operation of the latter inappropriate.

Advantages of light rail

Light rail systems are usually cheaper to build than heavy rail, since the infrastructure does not need to be considerable, and tunnels are usually not required as most metro systems. In addition, the ability to handle sharp curves and steep gradients can reduce the amount of work required.

Traditional streetcar systems and also newer light rail systems are used in many cities around the world because they generally can carry a larger number of people than any bus-based public transport system. They are also cleaner, quieter, more comfortable, and in many cases faster than buses. In an emergency, light rail trains are easier to evacuate than monorail or elevated rapid rail trains.

Many modern light rail projects re-use parts of old rail networks, such as abandoned industrial rail lines.

Disadvantages of light rail

Like all modes of rail transport, light rail tends to be safest when operating in dedicated right-of-way with complete grade separations. Nevertheless, grade separations are not always financially or physically feasible.

In California, the development of light rail systems in Los Angeles and San Jose caused a high rate of collisions between automobiles and trolleys during the 1990s. The most common cause was that many senior citizens were unfamiliar with light rail trolleys and often mistook the trolley "T" signal lights for left-turn signal lights. They would then make a left turn, right into the path of a trolley. The same high crash rate problem existed when the METRORail was first set up in Houston, Texas.

To reduce such collisions, brighter lights and louder warning klaxons have been added to many at-grade crossings. However, consequently, many people do not like to live next to light rail crossings because the noise makes them impossible to sleep. A more effective means of reducing or pre venting automobile-light rail collisions has been the installation of quad crossing gates at gate crossings. These gates block both lanes of a street when the gate closes. These prevent those driving auto mobiles from driving around the gates when they are lowered.

Monorail supporters like to point out that light rail trolleys are heavier per pound of cargo came than heavy rail cars or monorail cars, because they must be designed to avoid collisions with automobiles.

Monorail

A monorail is a metro or railroad with a track consisting of a single rail (in fact a beam) , in contrast to the traditional track with two parallel rails. Monorail vehicles are wider than the beam they run on.

Types and Technical Aspects

There are two major types of monorail systems. In suspended monorails, the train is located under the track, suspended from above. In the more popular straddle-beam monorail, the train straddles the rail, covering it on the sides. The straddle-beam style was popularized by ALWEG. There is also a form of suspended monorail developed by SAFEGE that places the wheels inside the rail.

Modern monorails are powered by electric motors and usually have tires, rather than metal wheels which are found on subway, streetcar (tram) , and light rail trains. These wheels roll along the top and sides of the rail to propel and stabilize the train. Most modern monorail systems use switches to move cars between multiple lines or permit two-way travel. Some early monorail systems—noticeably the suspended monorail of Wuppertal (Germany) , dating from 1901 and still in operation—have a design that makes it difficult to switch from one line to another. This limitation of the Wuppertal monorail is still mentioned at times in discussions of monorails in spite of the fact for both the suspended and straddle-beam type monorails the problem has been overcome.

Advantages and Disadvantages

The main advantage of monorails over conventional rail systems is that they require minimal space, both horizontally and vertically. The width required is determined by the monorail vehicle, not the track, and monorail systems are usually elevated, requiring only a minimal footprint for support pillars.

Owing to a smaller footprint they are more attractive than conventional elevated rail lines and visually block only a minimal amount of sky.

They are quieter, since modern monorails use rubber wheels on a concrete track.

Monorails can climb, descend and turn faster than most conventional rail systems.

Monorails are safer than many forms of at-grade transportation. As monorail wraps around its track and therefore cannot derail and unlike a light rail system, there is minimal risk of colliding with traffic or pedestrians.

I hey cost less to construct and maintain, in particular when compared to underground metro systems.

Monorails need their own track.

Although a monorail's footprint is less than an elevated conventional rail system , it is larger than an underground system 's.

A monorail switch by its very design will leave one track hanging in mid-air at any stated time. Unlike in the case of regular rail switches, coming from this track may cause derailing , with the additional risk of falling several meters to the ground.

Most countries (except Japan) do not have standardized beam specifications for monorails, so most tend to be proprietary systems.

In an emergency, passengers cannot exit at once because the monorail vehicle generally sits on top of its rail and there is no ledge or railing to stand on. They must wait until a fire engine or a cherry picker comes to the rescue. If the monorail vehicle is on fire and rapidly filling with smoke, the passengers may face an unpleasant choice between jumping to the ground (and possibly breaking bones in the process) or staying in the vehicle and risking suffocation. Newer monorail systems resolve this by building emergency walkways alongside the whole track (although this reduces the advantage of visually blocking only a minimal amount of sky) .

There are also some remaining concerns over the speed and capacity of monorails.

A Brief History of Magnetic Levitation

In the early 1900s, Emile Bachelet first conceived of a magnetic suspension using repulsive forces generated by alternating currents. Bachelet's ideas for EDS remained dormant until the 1960s when superconducting magnets became available, because his concept used too much power for conventional conductors. In 1922, Hermann Kemper in Germany pioneered attractive-mode (EMS) Maglev and received a patent for magnetic levitation of trains in 1934. In 1939-43, the Germans first worked on a real train at the ATE in Goettingen. The basic design for pratical attractive-mode maglev was presented by Kemper in 1953. The Transrapid (TR01) was built in 1969.

Maglev development in the U.S. began as a result of the the High-Speed Ground Transportation (HSGT) Act of 1965. This act authorized Federal funduing for HSGT projects, including rail, air cushion vehicles, and Maglev. This government largesse gave the U.S. researchers an early advantage over their foreign counterparts. Americans pioneered the concept of superconducting magnetic levitation (EDS,) and they dominated early experimental research. As early as 1963, James Powell and Gordon Danby of Brookhaven National Laboratory realized that superconductivity could get around the problems of Bachelet's earlier concepts. In 1966, Powell and Danby presented their Maglev concept of using superconducting magnets in a vehicle and discrete coils on a guideway.