毕业设计外文翻译--城市交通规划.doc

1、Urban transportation Planning An urban transportation system is basic component of an urban areas social，economic，and physical structure. Not only does the design and performance of a transportation system provide opportunities for mobility，but over the long term，it influences patterns of growth and

2、 the level of economic activity through the accessibility it provides to land. Planning for the development or maintenance of the urban transportation system is thus an important activity，both for promoting the efficient movement of people and goods in an urban area and for maintaining the strong su

3、pportive role that transportation can play in attaining other community objectives.There are several basic concepts about an urban transportation system that should be kept in mind. Most important，a transportation system in an urban area is defined as consisting of the facilities and services that a

4、llow travel throughout the region，providing opportunities for:(I)mobility to residents of an urban area and movement of goods and (2) accessibility to land .Given this definition，an urban transportation system can be further characterized by three major components: the spatial configuration that per

5、mits travel from one location to another; the transportation technologies that provide the means of moving over these distances; and the institutional framework that provides for the planning, construction, operation, and maintenance of system facilities.The Spatial Configuration of a Transportation

6、 SystemOne way to describe the spatial dimension of an urban transportation system is to consider the characteristics of individual trips from an origin to a destination. For example, a trip can consist of several types of movement undertaken to achieve different objectives. Travelers leaving home m

7、ight use a local bus system to reach a suburban subway station(a trip collection process)，proceed through the station to the subway platform (a transfer process)，ride the subway to a downtown station (a line-haul process)，and walk to a place of employment (a distribution process). Similarly，one can

8、view a home-to-work trip by car as consisting of similar segments，with the local street system providing the trip collection process, a freeway providing the line-haul capability，a parking lot in the central business district serving as a transfer point，and walking，as before，serving the distribution

9、 function.The facilities and services that provide these opportunities for travel，when interconnected to permit movement from one location to another，form a network. Thus，another way of representing the spatial dimension of an urban transportation system is as a set of road and transit networks. Eve

10、n in the smallest urban areas，where mass transit is not available，the local street network provides the basic spatial characteristic of the transportation system.The transportation system of a city can influence the way in which the citys social and economic structure, often called the urban activit

11、y system，develops. At the same time，changes in this structure can affect the ability of the transportation system to provide mobility and accessibility. Thus , the transportation system is closely related to the urban activity system and; historically, has been an important determinant of urban form

12、.Because of the relation between transportation and urban activities，many of the methods used by transportation planners depend on estimates of trips generated by specific land uses. The relation also suggests that the options available to public officials dealing with transportation problems should

13、 include not only those related directly to the transportation system, but also actions such as zoning that affect the distribution of land use, and thus influence the performance of the transportation system.The foregoing considerations point to two important principles for transportation planning:

14、 The transportation system should be Considered as an integral part of the social and economic system in an urban area.Viewed as a set of interconnected facilities and services designed to provide opportunities for travel from one location to another.The Technology of Urban Transportation The techno

15、logy of urban transportation is closely related to the spatial configuration of the transportation system in that the design transportation networks reflects the speed, operating , and cost characteristics of the vehicle or mode of transportation being used. Technology includes the means of propulsi

16、on, type of support，means of guidance，and control technique.The development and widespread use of electric streetcars in urban areas during the late nineteenth century was a technological innovation that initiated the transformation of most North American cities. The advent of the electric streetcar

17、 permitted urban areas to expand beyond the boundaries that had been dictated by previous transportation technologies (e. g.，walking，horse，horsecar)，spawning streetcar suburbs with dramatically lower residential densities along streetcar lines radiating from the central city. Whereas many industries

18、 had decentralized along railroad lines leading from the central city，and workers initially had to live near these factories, the introduction of streetcars now permitted more distant living.The success of the streetcar in providing access from selected suburban areas to central business districts w

19、as followed by public acceptance of a second major technological innovation-the automobile，powered by the internal combustion engine. Increasing consumer preferences for lower-density living and for an ability to travel beyond established urban boundaries sparked a phenomenal growth in automobile ow

20、nership and usage，beginning in the 1920s . The automobile continues and accelerated the evolution of urban structure started by the electric streetcar. Its availability permitted further expansion of urban areas and, more important, provided access to land between the radial streetcar and railroad l

21、ines leading into the central city.The technology of the internal-combustion engine，however, also led to the decline of other transportation modes used in urban areas by providing a less expensive and more flexible replacement for rail-based modes. While the automobile provided new opportunities for

22、 personal mobility and urban growth, motor buses rapidly replaced electric streetcars, to the extent that only five North American cities today still operate large-scale streetcar systems-Boston, Philadelphia, Pittsburgh, Toronto, and San Francisco (although this trend has reversed somewhat in recen

23、t years with new light rail systems in operation in Edmonton, Calgary, San Diego, and Buffalo). At the same time, the growth of private automobile use has dramatically reduced the use of public transportation in general, particularly since the end of World War II. According to the latest census figu

24、res, in 1980, 62. 3 million Americans normally drove alone to work each day, another 19 million car-pooled, and 6 million used public transportation.The technologies and the resulting modes available today for urban transportation are common to most cities but are often applied in different ways to

25、serve different purposes. It should be noted that certain types of modes are appropriate than others in serving different types of urban trips.The technological dimension of the urban transportation system suggests a third principle for urban transportation planning:Transportation planners must cons

26、ider the transportation system as consisting of different modes , each having different operational and cost characteristics.From; Michael D. Meyer and Eric J. Miller Urban Transportation Planning, 1984城市交通规划城市交通系统是市区的社会、经济、和物质结构的一个基本组成部分。一个交通系统的设计和实施不仅为流动性提供机会，并且从长远观点来看，通过它能对土地提供良好使用价值也使经济活动和发展受到益处

27、。这样，为了发展和维护城市交通系统而制定的规划是一项重要的活动，既是为了促进人和货物在市区的有效运转，同时也是为了保持交通在实现其他社团目标方而所能起到的强有力的支援作用。对于城市交通系统有几个基本概念是应该记住的。最重要的是,一个城市的交通系统被认为是包括交通设施和服务,这两者有助于贯穿全区的出行，并且为以下两方面提供机会:(1)居民的流通量和商品的运转，(2)对于土地的可达性。鉴于这种认识,城市交通系统可以进一步分解为以下三个部分:空间布置,可使一点到另一点的出行成为可能；交通技术,提供两地区运转的手段；机构的机制，提供交通系统设施的规划、建设、运营和维护。交通系统的空间布置 描述一个城市

28、交通系统的空间尺度的方式是考虑一个人由起点到目的地的出行特点。例如，出行可以包括为达到不同目的的几种类型的流动。离开家的出行者可以乘坐当地的公共汽车而到达另一个郊区地铁车站（出行集合过程），经车站转到地铁站台（换乘过程），乘地铁到达一个商业车站（沿线运行过程），然后步行到工作地点（分散过程）。相似的，人们可以把乘汽车由家到工作地点的出行看作是包括相似的过程，利用当地的街道系统实现出行集合过程，高速公路提供线路的出行能力，在商业中心区的停车场起到换乘点的作用，而步行与前面说的一样，起到分散作用。当提供这些出行机会的公共设施和服务集合起来,使从一个地点到另一个地点的运动成为可能时就会形成网络。这样

29、，表示一个城市交通系统的空间尺度的另一种方式是一组道路和公共交通的网络系统。甚至在不能利用公共交通的很小的市区内，当地的街道网络也会提供交通系统的基本空间特征。城市交通系统将会影响到城市的社会和经济结构（通常被称为城市活动系统）的发展方式。同时,这种结构的变化会影响交通系统提供流动性和可达性的能力。因此,交通系统是与城市活动系统密切相关的;从历史上看,城市交通系统曾经是一个决定城市形态的重要因素。由于交通和城市活动之间的关系，许多交通规划人员所使用的方法取决于特定的土地利用所产生的出行评估。这个关系还暗示可供与交通问题打交道的政府官员多采用的选择方案。而且也应该包括，例如，影响土地利用分布的区

30、域划分，并因此影响到交通系统特性的一些措施。上述的考虑指出用于交通规划的两个重要原则：被认为是市区社会和经济系统的一个完整部分。 被视为目的在于提供从一个地点到另一个地点出行机会的一套互相结合的交通设施和服务。城市交通的技术城市交通技术是同交通系统的空间布局紧密相关的，其中交通网设计反映车辆的速度、运行和费用特征所采用的交通模式。技术上包括推进的手段。支撑的类型引导的手段，以及控制技术。十九世纪晚期，在市区发展和广泛使用有轨电车是一项技术创新，启动了北美大多数城市的转型。有轨电车的出现使城市地区超出了之前运输技术（例如走路、骑马、马车）所限定的界限进行了扩展。产生了大量的居住密度明显很低的位于

31、由市中心辐射出去的电车电车路线沿线的“电车郊区”。与此同时，许多工业也从由市中心延伸出去的提路沿线疏散了，工人们起初需要在这些工厂附近居住，现在引进了电车，住的远也没有什么关系了。 在电车提供由经过挑选的郊区到中心商业区的道路取得成功后，接着是公众对于第二个重大技术革新，即对内燃机为动力的汽车的欢迎。消费者越来越多的对于低密度的居住生活的热爱，以及对于跨越已确定的城市边界出行能力的偏爱，促进了从二十年代开始的汽车购置和使用方便急剧增长。汽车的可用性促使市区进一步扩展，并且更重要的是，汽车为通向市中心的放射状电车线和铁路路线之间地区的可能性提供条件。 然而，由于内燃机技术提供了比有轨交通方式更为

32、廉价的和更为灵活的汽车，从而导致了市区内其他交通方式的衰落。在汽车为个人流通和和城市发展提供了新机会的同时，公共汽车很快取代了电车，以致目前只有五个北美城市还在使用大型电车系统，即波士顿、费城、匹茨堡、多伦多和旧金山（不过近年来这种趋势又有点逆转，新型“轻轨”系统正在埃德蒙顿、卡尔加里、圣地亚哥和布法罗运营）。于此同时，特别是自第二次世界大战结束以来，私人汽车使用的增长，一般来说已显著的使公共交通的使用缩减。根据最近的统计数字，在1980年有六千二百三十万美国人每天是自己驾驶汽车上班，另外有一千九百万人合伙使用汽车，而有六百万人乘用公共交通。当前可以应用的城市交通技术和交通模式，对于大多数城市

33、来说是通用的，但也常常以不同的方式应用，为不同的目的服务。应当注意到，某些交通方式较其他方式更适合于承担不同类型的城市出行。 城市交通系统的技术方面提出一个用于城市交通规划的第三个原则： 交通规划人员应当认为交通系统包括不同的交通方式，每一个方式具有不同的运营和费用特征。 摘自：迈克尔 D.梅耶和艾瑞克 J.米勒城市交通规划，1984Traffic signalsIn the United States alone ,some 250,000 intersections have traffic signals , which are defined as all power-operated

34、 traffic-control devices except flashers，signs，and markings for directing or warning motorists, cyclists，or pedestrians. Signals for vehicular，bicycle，and pedestrian control are pretimed where specific times intervals are allocated to the various traffic movements and as traffic actuated where time

35、intervals are controlled in whole or in part by traffic demand. Pretimed Traffic SignalsPretimed traffic signals are set to repeat regularly a given sequence of signal indications for stipulated time intervals through the 24-hr day. They have the advantages of having controllors of lower first cost

36、and that they can be interconnected and coordinated to vehicles to move through a series of intersections with a minimum of stops and other delays. Also, their operation is unaffected by conditions brought on by unusual vehicle behavior such as forced stops，which，with some traffic-actuated signal in

37、stallations may bring a traffic jam. Their disadvantage is that they cannot adjust to short-time variations in traffic flow and often hold vehicles from one direction when there is no traffic in the other. This results in inconvenience, and sometimes a decrease in capacity.Cycle length the time requ

38、ired for a complete sequence of indications, ordinarily falls between 30 and 120s. Short cycle lengths are to be preferred, as the delay to standing vehicles is reduced. With short cycles, however a relatively high percentage of the total time is consumed in clearing the intersection and starting ea

39、ch succeeding movement. As cycle length increases, the percentage of time lost from these causes decreases. With high volumes of traffic, it may be necessary to increase the cycle length to gain added capacity. Each traffic lane of a normal signalized intersection can pass roughly one vehicle each 2

40、.1s of green light. The yellow (caution) interval following each green period is usually between 3 and 6s，depending on street width，the needs of pedestrians, and vehicle approach speed. To determine an approximate cycle division, it is common practice to make short traffic counts during the peak per

41、iod. Simple computations give the number of vehicles to be accommodated during each signal indication and the minimum green time required to pass them. With modern control equipment, it is possible to change the cycle length and division several times a day, or go to flashing indications to fit the

42、traffic pattern better.At many intersections，signals must be timed to accommodate pedestrian movements. The Manual recommends that the minimum total time allowed be an initial interval of 4 to 7s for pedestrians to start plus walking time computed at 4 ft/s (1. 2m/s). With separate pedestrian indica

43、tors，the WALK indication(lunar white) covers the first of these intervals, and flashing DONT WALK (Portland orange ) the remainder. The WALK signal flashes when there are possible conflicts with vehicles and is steady when there are none. Steady DONT WALK tells the pedestrian not to proceed.If pedes

44、trian control is solely by the vehicle signals，problems develop if the intersection is wide, since the yellow clearance interval will have to be considerably longer than the 3 to 5s needed by vehicles. This will reduce intersection capacity and may call for a longer cycle time. On wide streets havin

45、g a median at least 6 ft (1. 8m)wide，pedestrians may be stopped there. A separate pedestrian signal activator must be placed on this median if pedestrian push buttons are incorporated into the overall control system.Coordinated MovementFixed-time traffic signals along a street or within an area usua

46、lly are coordinated to permit compact groups of vehicles called platoonsto move along together without stopping. Under normal traffic volumes，properly coordinated signals at intervals variously estimated from 2500 ft (0. 76km)to more than a mile (1. 6km) are very effective in producing a smooth flow

47、 of traffic. On the other hand，when a street is loaded to capacity，coordination of signals is generally ineffective in producing smooth traffic flow.Four systems of coordination-simultaneous, alternate，limited progressive, and flexible progressive-have developed over time. The simultaneous system ma

48、de all color indications on a given street alike at the same time .It produced high vehicle speeds between stops but low overall speed. Because of this and other faults，it is seldom used today.The alternate system has all signals change their indication at the same time，but adjacent signals or adjac

49、ent groups of signals on a given street show opposite colors. The alternate system works fairly well on a single street that has approximately equal block spacing. It also has been effective for controlling traffic in business districts several blocks on a said, but only when block lengths are approximately equal in both directions.