Movatterモバイル変換


[0]ホーム

URL:


Encyclopedia Britannica
Encyclopedia Britannica
SUBSCRIBE
SUBSCRIBE
SUBSCRIBE
History & SocietyScience & TechBiographiesAnimals & NatureGeography & TravelArts & Culture
Ask the Chatbot Games & Quizzes History & Society Science & Tech Biographies Animals & Nature Geography & Travel Arts & Culture ProCon Money Videos
Britannica AI Icon
printPrint
Please select which sections you would like to print:
verifiedCite
While every effort has been made to follow citation style rules, there may be some discrepancies.Please refer to the appropriate style manual or other sources if you have any questions.
Select Citation Style
Feedback
Corrections? Updates? Omissions? Let us know if you have suggestions to improve this article (requires login).
Thank you for your feedback

Our editors will review what you’ve submitted and determine whether to revise the article.

Advantages to individuals and communities

Where the automobile is a major competitor to masstransportation, the use of transit has declined, reducing revenues available to pay the costs of these systems and services, and—in a setting where government subsidies are essential for sustaining mass transit—political support has eroded as well. As more people rely on the automobile, their interest in directing public resources to improving the highway system dominates their concern for subsidizing transit.

News

For those who can use the automobile for quick and reliabletransportation, this trend simply represents the evolution of urban transport fromcollective riding to individual riding, from the economies of sharing a relatively high-speed service in a corridor where travel patterns are similar or the same, to the privacy of one’s own “steel cocoon,” which can go anywhere, anytime, without the need to coordinate travel plans with the schedule and routes of a transit operator attempting to serve large groups of people. The automobile has captured a large share (more than 95 percent by 1983) of urban trips in theUnited States, and only in some cities of more than two million people does the mass transportation share reach or exceed 10 percent of the trips.

If the automobile provides superior service for the majority of riders, why not let the market operate without government intervention, perhaps leading to thedemise of transit? While this has happened in some medium-size and small American cities, mass transportation can be important for a number of reasons.

First, some portion of the urban travel market is made up of people who cannot use the automobile to travel because they are handicapped, elderly, or too young to drive. Some people cannot afford to own and operate a car, and the young, the old, and the handicapped often fall into this category. If these people are to have the mobility essential for subsistence and satisfaction in their lives, some form of public transportation is necessary.

Second, transit provides acommunity with a way to move potentially large numbers of people while consuming fewer resources. A singlebus, if it is full (50 to 80 passengers), can carry as many people as 50 or 60 cars, which normally operate with fewer than 2 occupants. The bus requires less street space, equivalent to 2 or 3 automobiles, and, when it is full, it requires much less energy to move each person. Becauseemissions from internal-combustion engines are proportional to fuelconsumption, a full bus will produce lesspollution per person-trip than an automobile. Finally, because they are operated by professional drivers, buses have a lower accident rate than automobiles. Electric railrapid transit trains produce even lessair pollution and are far safer per person-trip than either automobiles or buses.

Transit, when it is well utilized, then, produces important benefits for the community: air-quality improvements, less land consumption than an auto-dependent transportation system, lower energy requirements, and lower accident costs. A single lane of an urban freeway may carry 5,000 persons per hour (seeTable). Alight rail transit line (electric trolley cars) on a separate guideway taking the same space as the highway lane might carry as many as 14,000 persons per hour. High-quality mass transportation serving dense employment and shopping areas, such as the central business district of acity or the downtown area of a suburban community, can help ensure the economic success of those areas by making it easier and less costly for large numbers of workers and shoppers to enter and leave. A successful transit system also reduces the need for downtown parking, making land available for more productive uses. Thus public transportation provides support for particular land development patterns, such as downtowns, and higher-density employment, educational, cultural, and retail activity centres.

Typical capacities of urban mass transportation modes
vehicle typeguideway typepersons per vehicle"train" length"trains" per houraverage speedpassengers per hour
seatedcrowdedlowhighlowhigh
autostreets1.231450900205402,700
autofreeways1.2319001,800301,0805,400
busstreets508011608504,800
busseparate5080113020502,400
light railstreets801003630101,4409,000
light railseparate901204430251,44014,400
heavy railseparate1001208440303,20038,400
commuter railseparate10015010112351,00018,000

These benefitsaccrue not only to transit travelers but also to other residents and to the owners of land and businesses. Indeed, a major benefit of mass transportation services goes to automobile travelers, who experience less congestion and shorter travel times. There is nomonetary market for these broadly distributed public goods produced by mass transportation. There is no practical way to sell clean air or lower accident rates to city dwellers to raise funds to subsidize and expand mass transit or to restrict access to these benefits only to those who pay for them. Somecommunities do raise revenues for transit and other purposes by levying special fees on properties particularly well-served by fixed-guideway transit (for example, in downtown areas or near rail stations) to capture some of the increased value produced by raising their accessibility with public transportation.

These public transportation benefits provide the justification for government subsidies. Their generation is strongly dependent on the utilization of mass transportation. The heavier the use of public transit, the larger will be the benefits produced. Yet even if only a small portion (5–10 percent) of the travel market uses transit in therush hours, a major reduction in congestion can result. On the other hand, buses and trains running nearly empty in the middle of the day, during the evening, or on weekends do not producesufficient benefits to the community to justify the high costs to provide these services.

Effects of publicpolicy

The benefits of mass transportation result from the utilization of these services: more utilization produces more benefits. Crowded buses and trains signify a smaller market share for the automobile, with its attendant air pollution, congestion, accidents, and excessive land consumption. Heavy utilization of mass transportation can produce a largerrevenue stream from passenger fares, which can help support these systems, either by reducingsubsidy requirements or, in a few very high-density travel corridors, actually covering all the costs of providing mass transportation.

There are a number of ways to increase and maintain mass transit ridership. These differ bycontext and government policy, and none offers guaranteed results. Keeping transit utilization high is much easier where competition from the automobile is limited. InThird World cities, where the automobile has never taken hold, transit, bicycles, and walking remain dominant modes. Cities are more densely settled, and work, shopping, and residential activities are closely intermingled so that trip distances are short. This encourages walking and the use of bicycles, with their low energy requirements. Even if mass transportation is slow and crowded, it may be the dominant mechanized travel option in such settings.

Cities in many developed countries in Europe and Asia have long-standing government policies that simultaneously controlled the growth of automobile ownership through high taxes on vehicles and their fuel; restricted land development to encourage high-density activity centres, including suburban new towns, as well as mixed land uses to keep trips short; and funneled a steady stream of public resources to subsidize masstransit operations and make capital investments to extend systems into new areas. These public investments in transit were generally not matched with similar investments in facilities for the automobile. Indeed, a number of cities around the world have restricted automobile travel to their downtown areas by defining auto-free zones (e.g., Gothenburg, Sweden), prohibiting the growth of parking, or charging high entry tolls for vehicles carrying only one or two people (Singapore).

In the United States the approach has been to allow thefree market, for both travel and land development, to determine the role of competing modes. Mass transportation does attract high market shares where the automobile is inherently less competitive, as, for example, travel todense downtown areas during the rush hours. In the central areas of larger cities such asNew York, Boston, Washington, Chicago, and even Los Angeles, street congestion can be intense and parking fees high. Where high-quality mass transportation is available (particularly rail service, which is as fast as or faster than the automobile), with frequent departures and high reliability, it can capture 50 to 80 percent of all travel to downtown in the rush hour. At other hours of the day, the mass transportation share of downtown travel may drop to 20 percent, and across the regions in which such cities are centred, the all-day transit share may be as little as 5 to 10 percent of trips.

Mass transit is critically important to the economic and social health of these cities, and it is also important in other communities where its market share is lower but its contributions to peak-period congestion reduction and mobilityassurance are significant. These effects provide the argument for public involvement in transit, through ownership, development, operation, and service subsidies. The key policy choices about mass transit in the United States concern how to spend public funds to produce these benefits, including decisions about capital investments for new and replacement technologies, the quantity and quality of services to offer, and how to pay for all of this.


[8]ページ先頭

©2009-2026 Movatter.jp