Unit 1 The Evolution of Transport交通工具的演化
The evolution of transport has been closely linked to the development of humankind throughout the earth’s history．Transport’s early function was to meet the basic need of hauling food supplies and building materials．But with the formation of tribes，then peoples，and finally nations,the societal and economic functions of transport became more and more complex。 At first there was mobility required for individuals，clans,households，and animals to protect them against，and to escape from，the dangers of natural disasters and tribal aggressions，and in the search for the best places to settle．As tribal groups formed and gradually established their geographical identity,transport was increasingly needed to open up regions for development，to provide access to natural resources，to promote intercommunal trade，and to mobilize territorial defense．When the first nations came into being，transport played a major role in establishing national integrity．
交通工具的演变紧密相连的人类在整个地球的历史发展.运输署早期功能是满足基本需要搬运粮食供应和建材等领域.但随着部落,然后人民，和最后国家形成，运输的社会和经济功能变得越来越复杂.在第一次有流动性所需的个人、 宗族、 家庭和动物保护他们免遭,和逃避危险自然灾害和部落的侵略行为,并在寻找最好的地方定居。部落群体形成和逐步确立其地理特征，运输日益需要开放地区的发展，以提供对天然资源,促进族裔间的贸易，并调动本土防卫的访问。当第一次的联合国应运而生时，运输发挥了重要的作用,建立民族气节
After basic societal needs had generally been attended to，local communities could increasingly devote their efforts to enhancing their economic，cultural，and technological development through trade links with other peoples and regions．Again，transport provided the mobility required for such intertribal， international，and finally intercontinental cultural exchange and trade．During all of this gradual development toward an organized human society，represented today through the international family of nations,transport as physical process of moving people and goods,thus promoting such development,continuously underwent technological and organizational changes．Such changes were induced by several factors and circumstances．In fact，today's transport in its various forms and organizational arrangements remains highly subject to changes in response to societal requirements and preferences．
基本社会需求大体上已照顾到后,当地社区可能会越来越多地致力于加强贸易联系通过与其他民族和地区经济、 文化和科技发展共同.再次，运输提供所需的这种部落之间、 国际和洲际最后的文化交流和贸易的流动。在所有有组织的人类社会,今天代表国际大家庭，交通工具的移动人员和货物，物理过程,从而促进这种发展，通过向此逐步发展的过程中不断发生了技术和组织的变化。这种变化是几个因素及环境所致。事实上，今天的各种形式和组织安排运输仍高度受回应社会需求和偏好的变化。
Clearly，the first and foremost criterion to be satisfied by transport was efficiency．For centuries,and particularly during the takeoff stages of local economics，society required reliable，fast,and low cost transport．The search for appropriate technologies was relatively unconstrained．There were times in human history when the demand for reliable and fast transport was especially pronounced,and quick solutions were required for national self-defense。 During such periods of local and international conflict, human ingenuity devised new transport technologies which often proved to be the decisive element for survival, and
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sometimes victory。 Subsequently refined and developed， such new technologies made it possible to better meet increasing transport demand, thus improving both economic progress and human welfare.
显然符合运输的首要准则是效率.几百年来,特别是在本地经济的起飞阶段期间，社会需要快速、 可靠、 和低成本的运输。寻找合适的技术是相对无约束.倍时,在人类历史上尤为突出的可靠、 快速的运输需求，并快速解决方案所需的国家自卫.在这样的地方和国际冲突的时期人类智慧制定新运输技术往往证明的生存空间,有时胜利的决定性因素。随后改进和发展，这种新技术使能够更好地满足日益增加的交通需求，从而提高经济进步和人类福祉。
The need for better strategic mobility induced efforts to improve sea and land transport。 This resulted in bigger and faster ships and more reliable and sturdy land vehicles. Eventually, self-propulsion was introduced， exemplified by steamboats， the railways, and then the automobile. Research and development in the transport field finally became an organized undertaking with specific goals and objectives。 As the result of the consequent concentration of talent and expertise， more and more sophisticated transport technologies evolved， such as the aircraft and, most recently， rocket propulsion。
需要更好的战略机动致努力提高海洋和陆地运输。这导致更大、 更快的船舶和更可靠和坚固的陆地车辆。最终,自航引入,蒸汽机船、 铁路和汽车的例子。在运输领域研发终于成为组织的承诺与特定的目标。作为随后浓度的人才及专业知识的结果，更多先进的传输技术如飞机和，最近,火箭推进发展。
The gradual evolution of increasingly sophisticated means of transport is manifested by today’ s transport systems， which include air， surface, and water transport. Special industry needs have led to the development of transport modes that have rather limited applications， such as pipelines, cables， and belts. Within current societal needs and preferences， as well as the economic requirements of cost effectiveness， the various existing transport modes generally fulfill rather specific functions.
今天的表现是逐渐演化的日益复杂的交通工具 ' s 运输系统，其中包括空中、 地面、 和海上运输.而是有限的应用程序如管道、 电缆和带的交通工具的发展导致特殊行业的需要。当前社会的需要和喜好，以及成本效益的经济上的要求，在现有的各种运输模式普遍达到而是特定的功能。
Although transport’s potential to meet effectively numerous societal mobility needs improved continuously， it became evident that such effectiveness had its price。 A number of transport technologies implied high energy consumption and required substantial capital inputs in production and operation。 As a result， several transport modes became expensive to the user。 This caused equity problems because charges required to cover operating costs were not affordable by all population groups， thus limiting their mobility and welfare。 Many governments chose to subsidize transport， but quickly realized that the budget implications often caused serious distortions in their national economies。
虽然运输的潜力以满足有效众多社会流动性需要不断改善,很明显这种有效性了它的价格。运输技术的一些暗示能耗高，所需大量资金投入生产和经营.因此，几个交通工具变得昂贵给用户。这造成了股权问题，因为业务费用所需的费用不是负担得起的所有人口群体，从而限制了他们的流动性和福利。许多国家的政府补贴交通工具,选择了，但很快意识到，所涉预算问题经常在自己国家的经济造成严重扭曲。
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Pollution caused by various transport modes gradually became another serious problem as world transport in most countries and the need to cope with rising volumes of commodity flows and person travel。 In several regions of the world having high population and industry concentrations, such detrimental impacts on the environment have reached high levels。 These effects of such damage yet are to be fully explored。
逐渐引起各种交通工具的污染成了另一个严重的问题，作为世界交通在大多数国家和应付日益增加的商品流动和人旅行的需要.过高的人口和产业的浓度在世界一些地区,这种对环境的不利影响已达到高水平.这种损害的这些影响还很充分探讨。
Finally, problems caused by dwindling world energy resources, particularly petroleum, have increasingly impeded transport services and operations. Most existing transport modes are critically dependent on petroleum derivatives for proper functioning. With unabated growth of demand for transport and a progressively limited supply of energy, the costs of providing transport have increased steadily。 In particular， the disproportion of petroleum requirements and petroleum supply has caused serious inflationary problems to arise in many countries。 Especially hard hit are countries with a partial or total dependence on an external petroleum supply， which have experienced growing deficits in their current accounts。
最后，特别是石油、 世界能源资源日益减少，所引起的问题越来越多地阻碍了交通服务和操作。大多数现有交通工具都依赖石油衍生品的正常运作。对交通的需求有增无减，逐步有限的能源供应提供运输的费用稳步增加。特别是石油需求和石油供应的非均衡性，引起严重的通胀问题在许多国家中出现.打击尤其是部分或全部依赖外部的石油供应,经历了它们的经常账户赤字不断增长的国家。
The transport sector’ s increasing inability to satisfy demand efficiently and equitably is a problem with which all nations have to cope in trying to advance economic and social progress. Energy—supply constraints， high capital and operating costs， often with excessive foreign—exchange components， and the seriousness of transport—related environmental pollution account in large part for this problem. But transport is and will continue to be an essential requirement for world development and human welfare。 There is no other choice but to look for alternatives to present transport systems or to modify the technical and operational characteristics of related modes so that energy consumption and costs wil1 be reduced and environmental impacts can be kept at a minimum. Obviously， the development of transport demand will have to be controlled.
运输部门 ' s 越来越无法满足需求，有效和公平地是，所有国家都必须应付在试图推动经济发展和社会进步的一个问题。能源供应约束、 较高的资本和经营成本，往往与过度外汇组件和运输有关环境污染帐户在很大程度上对这一问题的严重性.但运输是并将继续是世界的发展和人类福利的基本要求。有没有别的选择，但寻找替代目前的运输系统，或修改相关模式的技术和业务特点，使能源消耗及成本失败会减少和环境的影响可以保持在最低限度。很明显，发展的运输需求将不得不加以控制。
Notes
l。 As tribal groups formed and gradually established their geographical identity， transport was increasingly needed to open up regions for development，to provide access to natural resources,to promote intercommunal trade，and to mobilize territorial defense．
随着种族部落的形成和地理界线的逐步确定，开发新区域、开采新资源、发展社区间
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的贸易以及捍卫领地,这些都日益需要交通的发展.
2。 Again，transport provided the mobility required for such intertribal，international．and finally intercontinental cultural exchange and trade．
而且交通提供了诸如部落间、国际间乃至于洲际间便利的贸易和文化交流。
3．During all of this gradual development toward an organized human society，represented today through the international family of nations，transport as physical process of moving people and goods,thus promoting such development,continuously underwent technological and organizational changes．
在向有组织的人类社会的演变过程中,这种组织在今天是通过由各国组成的国际化大家庭表现出来的,交通作为人与货物移动的物理过程，电促进了这种发展，不断地经历着技术与组织方面的改变。
4．There is no other choice but to look for alternatives to present transport systems or to modify the technical and operational characteristics of related modes so that energy consumption and costs will be reduced and environmental impacts can be kept at a minimum． 没有别的办法,只有寻找新的交通替代手段或改变相关模式的技术与运行特点，才可以减少能源消耗和造价，对环境的影响也可以保持到最低程度。
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Unit 3 Transport Telematics
Text
Introduction
Transport telematics,also known as intelligent transport systems (ITS），are concerned with the application of electronic information and control to improve transport．Some new systems have already been implemented and the pace of implementation can be expected to quicken．With a crystal ball，we can foresee how a typical journey to work may look in 10 years time．
运输信息通讯，也称为智能交通系统 （ITS)，涉及电子信息与控制应用提高运输。一些新的制度已经实施和执行的步伐将会加快。有一个水晶球,我们可以预见典型之旅工作在 10 年时间里可能看起来.
You feel pleased with yourself that you have preceded your in—car navigation system with the coordinates of your final destination，and soon you are obtaining instructions on your best route with information updated from the local travel control center．
离开家里,渊前通过互联网检查您的旅游安排.通常您选择乘搭公共交通工具，您可以确定影响服务的任何中断和旅行的时间。这一次您选择乘搭车，因为你必须任命 1ater 在一天中在这些旧式商业公园是无法访问的公共交通工具之一。没有发生事件记录在你正常工作，所以您不想使用您的计算机路由型号为您选择最佳路线的路线上.
As you near your place of work，you are aware of roadside messages informing you of the next park and ride service．You choose to ignore these as you will need to make a quick getaway for your appointment．You then check that your travel card is clearly displayed inside the car;you don’t want to be fined for not having a positive credit for the city’s road pricing and parking service! The same card gives you clearance to your parking space；you activate your parking vision and co1lision control just to be sure of not scratching the MD’s car next to you． 一旦你的车，你头,高速公路和选择巡航控制、 车道支持和碰撞避免系统，使您可以专注于您最喜欢的电台服务.突然间，这是给你一件事你的路线上的信息的电台交通消息通道服务被中断.你不是惊讶的时候,在下一个路口，路边的可变信息标志 (VM） 确认这 ； 高速公路消息真的可信现在 Using transport elematics
All these information and control services， and many more besides, are discussed in the UK Government’ s consultation document。 One way of categorising these services is into the following application areas:
所有这些信息和控制服务和之外，更多的讨论,英国政府 ’ s 咨询文件。Categorising 这些服务的一种方法是到下面的应用领域：
① traffic management and control
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② tolling and road pricing ③ road safety and law enforcement
④ public transport travel information and ticketing ⑤ driver information and guidance ⑥ freight and fleet management ⑦ vehicle safety
⑧system integration
All these applications are being developed with assistance from research and pilot implementation programmes in Europe， USA and Japan。 Traffic management and control
Any traffic management and control system needs information on traffic flows， speeds， queues， incidents accidents, vehicle breakdowns， obstructions air quality and vehicle types, lengths and weights。 This information will be collected using infrared， radio， loop, radar， and microwave or vision detectors。 In addition， public and private organizations will provide information on planned events roadworks， leisure events， exhibitions。
The use to which this information is put depends on the objectives set for management and control. Network management objectives set for urban areas include:
①influencing traveller behaviour， in particular modal choice， route choice and the time at which journeys are made。
②reducing the impact of traffic on air quality。 ③improving priority for buses and LRT vehicles。
④providing better and safer facilities for pedestrians， cyclists and other vulnerable road users.
⑤restraining traffic in sensitive areas.
⑥managing demand and congestion more efficiently.
The software systems used will include control applications such as SCOOT， SCATS, SPOT and MOTION。 These are responsive systems， which control a network of traffic signals to meet these objectives. Automatic vehicle location and identification will provide information for giving priority or allowing access to certain vehicles only。
Interurban network management systems will have similar objectives but will make greater use of access control by ramp metering and other means, and of speed control and high—occupancy vehicle lane management。 Regional traffic control centers will advise motorist of incidents and alternative routes by VMS and by RDS—TMC， a signal FM radio service broadcasting localized traffic messages and advice to drivers。 Tolling and road pricing
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Interurban motorway tolling and urban road pricing provide another approach to meeting network management objectives while obtaining additional revenue that can be invested in transport. Singapore’s electronic zone pricing, the TOLLSTAR electronic toll collection and ADEPT automatic debiting smart cards are examples of such applications.
These systems rely on microwave or radio communication to an in—vehicle transponder in a smart card with detection of vehicle licence plates using image processing for enforcement purposes.
Public transport travel information and ticketing
Travel information is needed by passengers at home or office and also during their journey。 London Transport’s ROUTES computer-based service offers routing, timetable and fares information on all public transport services in London through public inquiry terminals. Real—time travel information is provided in London by the COUNTDOWN system which is being expanded to cover 4000 bus stops。 A similar system called STOPWATCH is available in Southampton as part of the ROMANSE project and is based on Peek’s Bus Tracker system which can detect buses using either radio beacons or GPS (Global Positioning System) which uses satellites to identify locations。
ROMANSE also includes TRIP lanner interactive enquiry terminals with touch screens providing travel information.
Problems with tickets for through journeys can be a deterrent for travelers choosing public transport。 Smartcard stored-value tickets can provide a single ticket for car parking and all legs of a journey served by different operators。 Driver information and guidance
Driver information systems include the RDS—TMC radio data system-traffic message channel， initially trialled between London and Paris in the PLEIADES project and elsewhere in Europe in similar EC-funded projects。 There is also the Traffic master service which uses infrared monitors to identify congestion and an in-car visual map—based screen to inform drivers of congestion.
Driver guidance systems aim to take this a step further by informing drivers of their route and giving guidance on navigation。 Communication between the control center and the vehicle can be by roadside beacon or by digital cellular radio network based on GSM（global system of mobile communications） as in SOCRATES。 Commercial products include Daimler Benz’s copilot dynamic route guidance system trialled in Berlin and Stuttgart and Philip’s Car Systems CARIN。 Similar products， such as the VICS advanced mobile information service, are commonly available in Japan。
Notes
1．Transport telematics，also known as intelligent transport systems (ITS），are concerned with the application of electronic information and control to improve transport．
交通运输远程信息处理系统,通常也被称为智能交通系统 (ITS系统），是利用电子信息和控制技术来改善交通的系统。
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2．On this occasion，you choose to travel by car as you have an appointment later in the day at one of those old—fashioned business parks that are inaccessible by public transport． 在这种情况下，当你在这天稍后有一个约会，而约会的地点是在公交车所不能到达的一个旧式商业停车场，那么你就可以选择乘坐小汽车前往。
3．Any traffic management and control system needs information on traffic flows,speeds,queues，incidents（accidents,vehicle breakdowns,obstructions)air quality and vehicle types,lengths and weights．
任何一种交通管理和控制系统都需要如下信息：交通流、车速、排队、交通事件（事故、车损、障碍物）、空气质量以及车辆的类型、长度与重量。 4．Interurban network management systems will have similar objectives but will make greater use of access control by ramp metering and other means,and of speed control and high-occupancy vehicle lane management．
城市间的网络管理系统将会有相似的目标，但是在通过匝道车流调节和其他一些方法来进行人口控制与速度控制以及高占有率车道管理方面也会起到很大作用。
5．These systems rely on microwave or radio communication to an in—vehicle transponder in a smart card with detection of vehicle license plates using image processing for enforcement purposes．
为实施管理的目的,这些系统依靠微波或无线技术与设在一张小卡片上的车载发射机应答器实现通信联系,这张卡片采用图像处理技术来探测车辆的驾驶执照.
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Unit 4 Public Transport Priority
Text
Design objectives
Public transport priority has to be seen in the context of an overall urban transport strategy with objectives which include not only improved bus or tram operation and restraint of car—borne commuting but also an enhanced environment for residents， workers and visitors. Measures proposed must serve all these objectives and yet also be demonstrably cost—effective and enforceable.
Typical design objectives for public transport priority measures include:
① to improve the conditions and reliability of bus operations through the introduction of appropriate bus priority measures.
② to alter the traffic balance in favor of buses at those locations where this can be properly justified。
③ to improve conditions for bus passengers at stops and interchanges.
④ to improve road safety generally and, in particular， for pedestrians, cyclists and people with disabilities。
⑤ to review, where appropriate, hours of operation of waiting and loading restrictions。
⑥ to establish and implement the coordinated and coherent application of waiting, parking and loading enforcement regimes on bus route corridors。 ⑦ to improve conditions for all road users and frontagers on bus route corridors。
Achieving these objectives often involves compromises between improving bus operation and the needs of local businesses and residents for reasonable access and of pedestrians and cyclists for safe and convenient movement。 Bus Priority Measures
Typical bus priority measures fall into four main categories：
① bus lanes and busways ② traffic and parking management measures ③ traffic signal control ④ bus stop improvements。
These are considered separately， but in practice the design for a bus route corridor will draw on measures from all these categories。
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(1) Bus lanes and busways
With-flow bus lanes are relatively commonplace。 They enable buses to avoid queues on congested sections of road by providing a lane marked and signed clearly and implemented under a traffic regulation order prohibiting use by general traffic。
Contraflow bus lanes enable buses to avoid circuitous routes， e.g. in a gyratory system， by permitting two-way movement for buses only over a road section。 The main disadvantage of a continuous contraflow bus lane is that it prevents kerbside access by vehicles, such as goods vehicles, that are not permitted to use it。
Busways and bus-only streets provide a dedicated track for use by buses。 Busways are either separate roadways or a part of a roadway but segregated from it, normally by kerbs.
(2) Traffic and parking management measures
These are typically no—entry and banned turn controls which allow buses and possibly
also cyclists to make a movement prohibited to other vehicles。
Finance and space permit。 One solution is for the highway authority to enable provision access route to commercial properties and to provide dropped kerbs and allow residents to gain access over the footway to parking within the curtilage of their properties。
(3) Traffic signal control
Traffic signal control include： ①Signal rephrasing for passive bus priority ②Selective
vehicle detection-active bus priority ③Overlap phases ④Queue relocation and traffic metering ⑤ Presignals and bus advance areas.
(4) Bus stop improvements
One of the major causes of delay in urban areas for buses and general traffic is
inconsiderate parking near bus stops. Buses have difficulty in gaining access to bus stops and subsequently rejoining the traffic stream。 Passengers have to resort to walking between parked cars to board a bus。
Sometimes the imposition of waiting and loading restrictions is inappropriate because this would prevent the reasonable use of lengths of road kerb by local residents and businesses。 One solution is to deter parking local to the bus stop and provide easier boarding for passengers by constructing bus boarders which consist of local extensions of the footway into the carriageway of about 1。0—2.0m。
The positioning of bus stops is often dictated by practicalities such as avoiding banks and post offices, where space for special deliveries is required, and avoiding creating poor sight lines for side road traffic。
Bus shelters are an obvious improvement at bus stops, providing protection from the weather. Timetable information should also be provided at bus stops in common static form listing the schedule of times of buses arriving at the stop and of reaching destinations, or as real-time information。
Passel kerbs are high-sided curved kerbs which allow bus drivers to align their vehicles
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precisely at bus stops. The great advantage is that boarding and alighting passengers have a near—level entry and exit to the vehicle， without the need to step onto the road。
Notes
1．Public transport priority has to be seen in the context of an overall urban transport strategy with objectives which include not only improved bus （or tram) operation and restraint of car—home commuting but also an enhanced environment for residents．workers and visitors． 公交优先应被看作是整个城市交通战略的一部分,它的目标不仅是改善公交(或电车)的运行和限制小汽车通勤交通，而且也是为居民、工作人员和游客提供一个更好的环境。
2．Achieving these objectives often involves compromises between improving bus operation and the needs of local businesses and residents for reasonable access and of pedestrians and cyclists for safe and convenient movement．
为了实现这些目标通常需要协调改善公交运行与各种要求之间的关系，这些要求包括地区商业和居民合理进入的需要、步行者和骑脚踏车的人的安全便利通行的需要。 3．One of the major causes of delay in urban areas for buses and general traffic is inconsiderate parking near bus stops．
随意在公交车站附近停车是引起市区公交车和总体交通延误的主要原因之一。 4．The positioning of bus stops is often dictated by practicalities such as avoiding banks and post offices,where space for special deliveries is required， and avoiding creating poor sight lines for side road traffic．
公交站点位置通常以实用性标准来选定，例如避开银行和邮局，因为那里要有进行特别递送活动的空间，而且也要避免造成路边交通视线不好的情况。
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Unit 6 Highway Systems and Functional Classifications
Text
Systems and classifications
The classification of highway into different operational systems，functional classes，or geometric features is necessary for communication among engineers，administrators， and the general public. Different classification schemes have been applied for different purposes in different rural and urban regions。 Classification of highways by design types based on the major geometric features(e．g．，freeways and conventional streets and highways)is the most helpful one for highway location and design procedures．Classification by route numbering（e．g．,U。S.，State primary,State secondary,and county numbering systems）,is the most helpful for traffic operations. Administrative classification （e．g．，State Federal aid primary,State Federal aid secondary，State primary，and state secondary）is used to denote the levels of government responsible for， and the method of financing， highway facilities．Functional classification，the grouping of highways by the character of service they provide,was developed for transportation planning purposes．Comprehensive transportation planning,an integral part of total economic and social development，uses functional classification as an important planning tool．The emergence of functional classification as the predominant method of grouping highways is consistent with the policies contained in this publication．
The concept of functional classification
A complete functional design system provides a series of distinct travel movements．The six recognizable stages in most trips include main movement，transition,distribution，collection， access， and termination． For example,a hypothetical highway trip uses a freeway，where the main movement of vehicles is uninterrupted，high—speed flow．When approaching destinations from the freeway,vehicles reduce speed on freeway ramps，which act as transition roadways．The vehicles then enter moderate—speed arterials distributor facilities that bring them nearer to the vicinity of their destination neighborhoods．They next enter collector roads that penetrate neighborhoods．The vehicles finally enter local access roads that provide direct approaches to individual residences or other terminations．At their destinations the vehicles are parked at an appropriate terminal facility． Each of the six stages of a typical trip is handled by a separate facility designed specifically for its function。 Because the movement hierarchy is based on the total amount of traffic volume， freeway travel is generally highest in the movement hierarchy， followed by distributor arterial travel, which is in turn higher in the movement hierarchy than travel on collectors and local access routes.
Although many trips can be subdivided into all of the six recognizable stages, intermediate facilities are not always needed. The complete hierarchy of circulation facilities relates especially to conditions of low-density suburban development, where traffic flows are cumulative on successive elements of the system。 However， it sometimes is desirable to reduce the number of components in the chain。 For instance, a large single traffic generator may fill one or more lanes of a freeway during certain periods。 In this situation, it is expedient to lead traffic directly onto a freeway ramp without introducing arterial facilities that unnecessarily mix already—concentrated traffic flows with additional vehicles。 This deletion of intermediate facilities does not eliminate the functional need for the remaining parts of the flow hierachy or the functional design components, although it
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may change their physical characters。 The order of movement is still identifiable。
The failure to recognize and accommodate by suitable design each of the different trip stages of the movement hierarchy is a prominent cause of highway obsolescence. Conflicts and congestion occur at interfaces between public highways and private traffic-generating facilities when the functional transitionsare inadequate. Examples are commercial driveways that lead directly from a relatively high—speed arterial into a parking aisle without intermediate provisions for transition deceleration and arterial distribution or， more seriously， freeway ramps that lead directly into or from large traffic generator such as major shopping centers。
Inadequate acceptance capacity of the distributor arterial or internal circulation deficiencies within the traffic absorber create the danger that traffic may back up onto the freeway。 Successful internal design that provides facilities to accommodate all the terminal parking facility will alleviate such a situation。
In the case of the freeway leading to a large traffic generator， deceleration from rapid movement on the freeway occurs on the exit ramp。 Distribution to various parking areas is then accomplished by primary distribution-type roads or lanes within the parking facility。 These roads or lanes supplant the distributor arterial function。 Collector-type roads or lanes within the parking facility may then deliver segments of the entering flow to individual parking space terminals， and then becomes the equivalent of an access street。 Thus， the principal functions within the hierarchal movement system are recognizable。 It can be pointed out that each functional category also is related to a range of vehicle speeds。
The same principles of design are also relevant to terminal facilities that adjoin distributor arterials or collectors. The functional design of the facility includes each movement stage， with internal circulation in the terminal designed to accommodate the order of movement. The necessity of designing for all stages of the movement hierarchy varies with the size of the traffic generator。 For relatively small generators， two or more stages may be accommodated on the same internal facility。 For larger traffic generators， each movement stage must have a separate functional facility.
To determine the number of design components necessary， the customary volumes of traffic handled by public streets of different functional categories can be compared. The volume range on private internal facilities can be related to the comparable range on public streets。 These volumes may not be directly comparable, in as much as the physical space available within a private facility is smaller and the standards of operation are necessarily quite different. However， the same principles of flow specialization and movement hierarchy can be applied.
Some further examples may demonstrate how the principles of movement hierarchy are related to a logical system of classification of traffic generation intensity. At the highest practical level of traffic generation a single generator fills an entire freeway， and for this condition， intermediate public streets could not be inserted between the generator and the freeway， so the various movement stages must be accommodated internally with appropriate design features. At the next level of traffic generation a single traffic generator could fill a single freeway lane； it is then appropriate to construct a freeway ramp for the exclusive use of the generator without intervening public streets. At still smaller volumes it becomes desirable to combine the traffic from several generators with additional traffic before the flow arrives at a freeway entrance ramp. The road performing this function then becomes a collector facility， accumulating these small flows until a traffic volume that will fill the freeway ramp is reached.
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Similar principles can be applied at the distributor arterial level of service。 If a given traffic generator is of sufficient size， an exclusive intersection driveway for that generator is justified. In other cases an intermediate collector street should combine smaller traffic flows until they reach a volume that warrants an intersection along the distributor。 The same theory can be applied with regard to the criteria for direct access to the collector street。 A moderately sized traffic generator usually warrants a direct connection to the collector without an intermediate access street； however， in a district of single—family residences a local access street should assemble the traffic from a group of residences and lead it in to a collector street at a single point of access。 In practice， direct access to arterials and collectors must be provided from commercial and residential properties， particularly in established neighborhoods.
In short， each element of the functional hierarchy can serve as a collecting facility for the next higher element， but an element must be present only where the intermediate collection is necessary， to satisfy the spacing and traffic volume requirements of the next higher facility。 By defining the spacing and volume requirements for a system element, it is possible to determine in which cases it is necessary to use the full system and in which eases intermediate elements may be bypassed。
Notes
1．Comprehensive transportation planning,an integral part of total economic and social development，uses functional classification as an important planning tool．
综合交通规划是整个社会和经济发展的一个主要组成部分,它把功能划分作为一个重要的规划工具。
2．The vehicles finally enter local access roads that provide direct approaches to individual residences or other terminations．
车辆最终进入局部性支路，这些道路可以直接抵达个人居所或其他目的地。
3．Inadequate acceptance capacity of the distributor arterial or internal circulation deficiencies within the traffic absorber create the danger that traffic may back up onto the freeway．
集散性干道通行能力的不足或交通吸引区内部循环的缺陷会产生车流返回高速公路的危险。
4．At the next level of traffic generation a single traffic generator could fill a single freeway lane；it is then appropriate to construct a freeway ramp for the exclusive use of the generator without intervening public streets．
在一定的交通生成水平下，由单一的交通发生源产生的交通流可能会充满单条高速公路车道，因此适合设置一条专门为这一发生源而用的匝道,从而使之不会干扰公共道路。 5．In practice， direct access to arterials and collectors must be provided from commercial and residential properties，particularly in established neighborhoods．
实际上，这些主干路和集散道路必须从商业和居民财产、特别是在邻近地带建造住宅的人的利益出发，提供直接的出人口。
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Unit 13 Traffic Surveys
Text
Traffic engineering is used to either improve an existing situation or， in the case of a new facility, ensure that the facility is correctly and safely designed and adequate for the demands that will be placed on it.
In an existing situation we have to know the present day demands and patterns of movement， so that the new measure can be designed adequately. With a new road or facility， there is obviously no existing demand to base the design on； therefore， we have to estimate the expected demand。 If a new facility replaces or relieves existing roads, for example a bypass or a new cycle track， we can estimate the proportion of traffic that could be expected to transfer using a traffic assignment。
If the facility is completely new, for example a road in a new development, then the expected traffic and hence the scale of construction needed has to be estimated another way。 This is usually done by a transport impact analysis which will seek to assess the likely level of traffic by reference to the traffic generated by similar developments elsewhere。 In either case the starting point will be a traffic survey。
The main reason for undertaking a traffic survey is to provide an objective measure of an existing situation。 A survey will provide a measure of conditions at the time that the survey was undertaken. A survey does not give a definitive description of a situation for ever and a day and, if the results are to be used as representative of ' normal’ traffic conditions, the survey must be defined with care and the information used with caution。
Traffic flows also tend to vary by day of the week。 On a typical urban road traffic flows tend to build during the week to a peak on Friday。 Flows are lower at the weekend, when fewer people work and lowest on Sunday； although the introduction of Sunday trading has affected the balance of traveling at the weekend.
The variation in pattern of travel over the year depends a great deal upon location。 In urban areas, which are employment centers, flow drops during the summer period when schools are closed and workers tend to take annual holidays。 This is balanced by a reverse trend in holiday areas。 Where traffic flows increase dramatically in July and August， and roads which are adequate most of the year become heavily congested。 The effect can be less dramatic on interurban roads， other than those providing access to holiday areas， as, to an extent, the decline in interurban business travel during the summer is offset by tourism.
The information above shows that the pattern of flow on any road can be highly variable and， in deciding when and where to undertake a traffic survey， it is important to ensure that the survey provides a fair measure of the traffic conditions that are being studied. To take the example of the road in a tourist area， a traffic survey on August bank holiday would measure peak traffic conditions。 As these levels occur only one or two days a year there would be little point value in using this data as a basis for design， as the scheme would be for traffic conditions most of the time。
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Generally, traffic surveys should not be planned to measure the peak of the peak but to measure the' normal' peak conditions。 Trunk road surveys may require a full year’ s survey of traffic so that the 50 th(30th or 200th) highest hourly flow can be determined, and used as the basis for design.
The starting point in defining a traffic survey is to decide what question has to be answered and choose the type of survey accordingly. If the survey is not adequately planned， there is a danger that wrong data will be collected and the traffic situation will not be correctly understood。 The only exception to this rule occurs when one is faced with a complex situation where it may not possible， at first， to adequately understand what is going on， in terms of traffic flow and circulation。 In these circumstances the traffic survey is providing evidence which will not only be used to quantify behavior， it may also be used to define it。
Some surveys are adequate for measuring traffic flow and direction of movement at a single point， or at a single junction。 However， if we wish to understand movement over a wider area， then other methods have to be used. Three techniques are described below， one for surveys and two covering origin and destination surveys.
（ 1 ) Surveys
We may wish to understand how traffic is circulating in a limited area。 This could be， for example, a complex gyratory system， a residential area where we suspect that there may be rat-runs， or even a town center ring road where we wish to understand if traffic uses the ring road or passes through the town center.
The technique used is to record the registration mark of each vehicle as it enters and leaves the system being studied and then to match the registration marks, to establish how a vehicle traveled through the road system being studied. It is not normally necessary to record the full registration mark。
（2）Origin and destination survey
The alternative way to establish where drivers are traveling is to ask them， using an origin and destination (O＆D) survey. Various types of O&D surveys are used as a part of the wider transport planning process. However， this is beyond the scope of this paper and is not explored here。 The standard techniques are roadside interview surveys and self—completion questionnaires。
In most cases it will be impossible to carry out a 100％ survey of drivers and so we must rely on a response from a sample of drivers in the traffic flow. Clearly, if the survey results are to be relied on， sample should be unbiased with all types of vehicles and movements represented.
(3) Roadside interview surveys
At a roadside interview survey, a sample of drivers are stopped at the side of the road and asked their origin and destination， plus any other data which could be of relevance， such as journey purpose.
Notes
1．Traffic engineering is used to either improve an existing situation or, in the case of a new facility,to ensure that the facility is correctly and safely designed and adequate for the demands that
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will be placed on it．
交通工程既可以用于改进现有设施的交通状况,也可在新建交通设施时用，以确保该设施设计的安全性和准确性，并适应在该设施上将会产生的交通需求.
2．This is usually done by a transport impact analysis which will seek to assess the likely level of traffic by reference to the traffic generated by similar developments elsewhere．
通常采用交通影响分析来完成该项任务，交通影响分析会根据其他类似发展环境下产生的交通情况来评价可能的交通状况。
3．A survey does not give a definitive description of a situation for ever and a day and，if the results to be used as representative of ‘normal’ traffic conditions，the survey must be defined with care and the information used with caution．
调查不可能对长期的和一天的交通状况给出确定的描述，如果要用调查结果作为一般交通状况的代表的话，则须对该调查作确切说明,采用资料时也须慎重。
4．At a roadside interview survey，a sample of drivers are stopped at the side of the road and asked their origin and destination，plus any other data which could be of relevance，such as journey purpose。
在路边访问调查中，在路边抽样拦停一些车辆驾驶员,询问他们的起讫点以及所有其他相关资料，例如出行目的等.
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Unit 16 Four-Step Planning Procedure
Text
Urban transportation planning calls for more than just providing for the safe and efficient movement of people and goods. It involves the planning of transportation facilities or operations responsive to the goals of the community being served。
Identifying goals and seeing that plans are responsive to them can be difficult。 One way to bridge gaps between community viewpoints and the planner's technical processes is to set up an interlocking set of guiders that proceed from the general to the particular。 A hierarchy of values, goals， objectives, criteria and standards has been suggested， in which：
（1）Values are basic social drives that govern human behavior. They include the desire to survive, the need to belong， the need for order， and the need for security。
（2) Goals define conditions to be achieved， as environments favorable to maximizing values。 They can be stated, although the degree of their achievement may not be definable。 ’Equal opportunity’, for example, is a goal based on the values of security and belonging.
(3) Objectives are specific， attainable， and measurable。 In relation to the goal of equal opportunity， a transportation objective might be equal public transportation costs for all citizens regardless of location within the city。
(4)Criteria are the measures or tests to show whether or not objectives are attained. For example, the ratio of transit fares to personal income may be the criterion for determining whether or not the foregoing equal—transportation—cost objective has been met.
（5) Standards establish a performance level that must be equaled or surpassed。 To continue with the previous example， transit service within 1/4 mi of every residence would be a standard。 To explain and develop land use/travel relationships， four steps of trip generation, trip distribution, modal split, and traffic assignment are typically followed。 Trip generation
In major urban studies, trip generation mathematically relates survey—reported trip making to household characteristics and other land—use types, using statistical procedures to establish trip rates， such as person-trips per household。 The trip-distribution procedure usually determines the necessary level of detail。 In some studies， trip generation expressed as auto driver trips per 1000 ft of floor space will be satisfactory. Even more simply， reported trip rates published in Trip Generation or other sources may be applied to a land-use data base. Trip distribution
The preceding step of trip generation typically develops a tabulation of trip origins or trip attraction by small areas。 Trip distribution links trip origins to destinations in order to produce estimates of network travel。 Several models may be used： among these are the Fratar method， the intervening opportunities model， and the gravity model. In the latter technique， which is most commonly used， trip volumes from zone A to zone B are calculated as a direct function of the
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product of trip—end quantities in both zones and as an inverse function of the time or distance separating them. Typically， trips will be stratified into groups by trip purpose and the distribution for each group will be determined independently. Grouping might include：
(1）Home-based trips to work, shopping， social—recreation， schools， and all other purposes (2） Nonhome—based trips （neither origin nor destination at home ） （3） Truck trips （4） Taxi trips
The model's performance is first verified by using the network and traffic assignment techniques see if model—produced O-D patterns and network loadings are comparable to those obtained from trip surveys and their assignment to the network. Once calibrated， the model is then ready to develop travel patterns based on forecast data for the target planning year。 Modal split
The trip—generation and trip—distribution steps may or may not be concerned with the problem of converting person-trips into automobile trips or transit passenger trips。 Where mode choice is essential, several procedures are available to determine the split either before or after the trip—distribution step 。 Trip diversion based on travel-time differences between modes is the basis for some methods， but it is being supplanted by techniques relying heavily on trip-maker or household characteristics。 Traffic assignment
The fourth step brings the outputs from preceding tasks to a coded transportation network。 The estimates from the trip-generation step are loaded on the network： from zone—level ’loading nodes'。 They are then routed over those links giving the shortest time paths to zonal destinations as determined by the trip-distribution model. If certain links become overloaded as a result of assignments， the model may use 'capacity—restraint’ procedures to limit the volumes， usually by increasing link travel times or reassigning subsequent trips to alternative paths。 When the process is done， the results can be produced as tabulations of link loadings or plotted graphically。 Depending on available subroutines， other results, such as link and area volume/capacity ratios，vehicle—miles， and vehicle-hours of travel， or tabulations of O-D matrices using selected links, may also be derived。 Similar procedures apply to person—trips assigned to transit networks 第四步从前面的任务使输出编码的交通网络。在网络上加载的估计数字从交通生成步骤： 从区域级 ’加载节点'.然后将它们路由通过这些链接给纬向目的地所确定的出行分布模型的时间最短路径。如果某些环节成为重载分配的结果,模型可以使用 ’能力约束型' 程序限制卷，通常通过增加链接旅行时间或重新分配到备用路径的后续行程.当该进程完成后时，可以作为表格的链接荷载产生结果或绘制图形.取决于可用的子例程，也可能派生其他结果，例如链接和区域卷/容量比率、 行驶里程,和车辆小时的旅行或使用所选的链接，O D 矩阵的表格。类似的程序适用于分配给网络的过境人次
Notes
1．One way to bridge gaps between community viewpoints and the planner’s technical processes is to set up an interlocking set of guiders that proceed from the general to the particular．
一种将公众观点与规划者的技术过程相衔接的办法是建立一套相互关联的由一般到特殊
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的指导方针.
2．To explain and develop land use／travel relationships,four steps of trip generation，trip distribution，modal split，and traffic assignment are typically followed．
为了解释及研究土地利用和出行之问的关系，典型的做法只遵循出行产生、出行分布、方式划分和交通分配这四个步骤.
3．In major urban studies,trip generation mathematically relates survey—reported trip making to household characteristics and other land—use types,using statistical procedures to establish trip rates,such as person—trips per household．
在大多数城市研究中，出行产生用统计学程序得到出行率，例如每个家庭的出行人次，为调查报告中的出行与家庭特征和其他土地利用类型建立数学关系.
4．The model's performance is first verified by using the network and traffic assignment techniques to see if model—produced O-D patterns and network loadings are comparable to those obtained from trip surveys and their assignment to the network。
模型的性能首先要通过路网和交通分配技术看其产生的起讫点方式和路网荷载是否与出行调查得到的和实际分配到路网上的情况相吻合来验证。
5．If certain links become overloaded as a result of assignments, the model may use “capacity—restraint” procedures to limit the volumes usually by increasing link travel times or reassigning subsequent trips to alternative paths．
如果某些线路由于交通分配的结果流量过大，模型会选择“容量限制”法,通过增加路段出行时间或重新分配相关出行到备选路径上来限制流量。
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Unit 17 Highway Capacity
Text
Capacity and levels of services
A principal objective of capacity analysis is the estimation of the maximum number of people or vehicles that can be accommodated by a given facility in reasonable safety within a specified time period. However, because facilities generally operate poorly at or near capacity, they are rarely planned to operate in this range。 Accordingly， capacity analysis also provides a means of estimating the maximum amount of traffic that can be accommodated by a facility while maintaining prescribed operational qualities。
Capacity analysis is, therefore， a set of procedures for estimating the traffic-carrying ability of facilities over a range of defined operational conditions. It provides tools for the analysis of existing facilities and for the planning and design of improved or future facilities。 The definition of operational criteria is accomplished by introducing the concept of levels of service。 Ranges of operating conditions are defined for each type of facility and are related to amounts of traffic that can be accommodated at each level.
Ideal conditions
Many of the procedures in this manual provide a formula or simple tabular or graphic presentation for a set of specified standard conditions, which must be adjusted to account for any prevailing conditions not matching those specified. The conditions so defined are often ideal conditions。
In principle， an ideal condition is one for which further improvement will not achieve any increase capacity. Ideal conditions assume good weather， good pavement conditions， users familiar with the facility， and no incidents impeding traffic flow. Specific ideal conditions are identified in each chapter. Examples of ideal conditions are given below for uninterrupted flow facilities and for intersection approaches.
Ideal conditions for uninterrupted flow facilities include the following： lane widths of 12ft; clearance of 6ft between the edge of the travel lanes and the nearest obstructions or objects at the roadside and in the median； design speed of 70mph for multilane highways， 60mph for two—lane highways; only passenger cars in the traffic stream; level terrain。 Ideal conditions for intersection approaches include the following： lane widths 12ft; level grade； no curb parking on the intersection approaches； only passenger cars in the traffic stream and no local transit buses stopping in the travel lanes； all vehicles traveling straight through the intersection； intersection located in a non—central business district area; no pedestrians; at signalized intersection approaches， green signal available at all times。 In most capacity analyses， prevailing conditions are not ideal， and computations of capacity， service flow rate， or level of service must include predictive adjustments to reflect
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this absence of ideal conditions. Prevailing conditions are generally categorized as roadway, traffic， or control conditions。 Vehicle control and technology represent conditions that change in the long term.
Roadway conditions
Roadway factors include geometric conditions and design elements. In some cases， these factors influence the capacity of a road, whereas in others， the factors may affect a measure of effectiveness， such as speed， while not affecting the capacity or maximum flow rate that can be carried by the facility.
Roadway factors include the following： ①The type of facility and its development. ②Lane widths。
③Shoulder widths and lateral clearances。 ④Design speed
⑤Horizontal and vertical alignments。 ⑥Availability of queuing space at intersections
The type of facility is critical. The existence of uninterrupted flow， the presence of medians, and other major facility type factors significantly affect flow characteristics and capacity。 The development environment has also been found to affect the performance of two—lane roadways， multilane highways, and signalized intersections.
Lane and shoulder widths can have a significant impact on traffic flow。 Narrow lanes cause vehicles to travel closer to each other laterally than most drivers would prefer。 Motorists compensate by slowing down or observing larger longitudinal spacing for a given speed, which effectively reduces capacity， service flow rates, or both。
Narrow shoulders and lateral obstructions have two important impacts。 Many drivers will steer away from roadside or median objects they perceive to pose a hazard. This action brings them laterally closer to vehicles in adjacent lanes and causes the same reactions as those exhibited in narrow lanes.
Restricted design speeds affect operations and level of services； drivers are forced to travel at somewhat reduced speeds and to be more vigilant in reacting to the harsher horizontal and vertical alignments resulting from a reduced design speed。 In extreme cases， the capacity of multilane facilities has been found to be affected by low design speeds。
The horizontal and vertical alignment of a highway depends greatly on the design speed used and the topography through which the roadway must be constructed. Procedures for uninterrupted flow facilities categorize the general terrain of a highway as follows：
（ 1 ） Level terrain
Any combination of grades and horizontal and vertical alignment that allows heavy vehicles to maintain approximately the same speed as passenger cars; this terrain generally
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includes short grades of no more than 1 to 2 percent。
(2） Rolling terrain
Any combination of grades and horizontal or vertical alignment that causes drivers of heavy vehicles to reduce speeds to substantially belowthose of passenger cars， but dose not require operation at crawl speeds for any significant length of time.
(3） Mountainous terrain
Any combination of grades and horizontal and vertical alignment that causes drivers of heavy vehicles to operate at crawl speeds for significant distances or at frequent intervals. Crawl speed is the maximum sustained speed that heavy vehicles can maintain on an extended upgrade of a given percent.
These definitions are general and depend on the particular mix of heavy vehicles in the traffic stream。 In general, as terrain becomes more severe， capacity and service flow rates are reduced。 This impact is significant for two—lane rural highways， where the severity of terrain not only affects the operaing capabilities of individual vehicles in the traffic stream, but also restricts the opportunities to pass slow—moving vehicles in the traffic stream。
In addition to the general impacts of terrain, isolated upgrades of significant length may have a substantial effect on operations。 Heavy vehicles slow significantly on such upgrades， creating operational difficulties in the traffic stream and inefficient use of the roadway。 Grades also may have a major impact on the operation of intersection approaches; vehicles must overcome both the grade and the inertia of starting from a stopped position at the same time。
Notes
1．Accordingly,capacity analysis also provides a means of estimating the maximum amount of traffic that can be accommodated by a facility while maintaining prescribed operational qualities.
因此，通行能力分析也提供了一种用于估算某种设施在保证规定的运行质量条件下所能适应的最大交通量的方法。
2. In principle, an ideal condition is one for which further improvement will not achieve any increase in capacity．
原则上,理想条件是指无论怎样改善也不能提高设施通行能力的条件。
3．Ideal conditions for uninterrupted flow facilities include the following：lane widths of 12ft;clearance of 6 ft between the edge of the travel lanes and the nearest obstructions or 0bieets at the roadside and in the median； design speed of 70mph for multilane highways，60mph for two-lane highways;only passenger cars in the traffic stream；level terrain． 非间断流设施的理想条件包括：车道宽12英尺,路边或中央分隔带上障碍物距行车道边缘宽6英尺，多车道公路设计车速为70英里／小时，双车道公路设计车速为60英里／小时，交通流中全部为小客车,平原地形。
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4．Any combination of grades and horizontal and vertical alignment that causes drivers of heavy vehicles to operate at crawl speeds for significant distances or at frequent intervals． 使重型车辆在相当长的距离内或频繁地以爬坡速度行驶的坡度和平、纵线形的任何组合。
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Unit 18 Highway Safety
Text
Trends
Highway traffic accidents， injuries, and deaths continue as the major safety problem in transportation.
Passenger automobiles are the type of vehicle having the largest percentage of fatalities。 Trucks have a greater involvement in multiple—vehicle crashes than does any other vehicle type。
Most fatal accidents involving motorcycles result in the death of the motorcycle occupant rather than an occupant of the other vehicle involved。 Similarly， in fatal collisions involving a truck and another vehicle, the fatality usually occurs in the other vehicle。
The largest percentage increases in motor vehicle traffic fatalities from 1977 to 1978 were in the categories of pickup truck and van occupants （13%) and motorcyclists (9。6％）. In these two categories, increases in the popularity of these vehicles are reflected in accident figures。
As the number of vehicle—miles traveled increases， and fatalities remain relatively stable (except for the fuel shortage period of 1973 — 1974）， fatality rates show a long-term decline。 The 3—year period 1976 - 1978, however， showed a gradual increase.
Over a longer period of time， with data from 1925， the general， long-term trends can be seen more clearly. The fuel shortage of 1973 — 1974, and imposition of the 55 mph speed limit， are seen to have had very temporary and limited effects on the generally upward trend of vehicle-miles driven and number of deaths。 The trend in the death rate may or may not have stabilized at a rate below 3。5 per 100 million vehicle-miles or may be increasing again。
Cause and Problem Areas
Collisions between motor vehicles are seen to be the largest single category of traffic fatalities。 ' Non—collision' accidents (many of which involve collision with a fixed object） are second.
Identifiable problem areas in highway traffic safety include： ① Pedestrian—vehicle conflicts ② Vehicle-vehicle conflicts
③Interactions of differently sized vehicles ④Inadequate or impaired driving ability
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交通工程专业英语
⑤Railroad—highway grade crossings
⑥Inadequate communication with the driver (signs， markings， signals）， and between drivers ⑦Deterioration of physical plant (reduced maintenance on highways and bridges） ⑧Roadside safety hazards
About 18％ of the motor—vehicle-related deaths are pedestrian deaths (about 8000 in 1978）。 Intersection accidents account for the major proportion of urban accidents.
The trend toward smaller automobiles and larger trucks has created a major problem on the highways, a problem that is aggravated by increases in motorcycle use； on many roads， bicycles and mopeds are added to the problem。
A majority of accidents are still attributed to ’ human error', or driver impairment through the use of alcohol or other drugs, even though it is clear that only minor advances can be expected in controlling this problem。 At the same time, improvements in vehicle design and control, and highway design and control measures, have not been exhausted.
The railroad-highway grade crossing problem is one that should be clearly understood by transportation engineers and treated as an illogical intersection of two vastly different modes。 Although it is economically impractical to eliminate all grade crossings within a brief time period， grade separation is the only positive engineering solution available and should be scheduled over a reasonable period。 Other treatments for rail—highway grade crossings are interim solutions at best。
Poorly designed， placed， and maintained signs, poorly timed signals， and poorly maintained or nonexistent markings still abound in many areas of the country。 It was stated in 1979 that bridges in the united states ’are collapsing at the rate of one a day’。And by 1979, 12 years after the U。S. House of Representatives’ Subcommittee on Federal aid Highways hearings pointed out the roadside—hazards or 'booby-traps' problem on high speed roads, deaths attributable to this kind of single—vehicle accident were again approaching 17,000 per year。
Notes
1．The trend toward smaller automobiles and larger trucks has created a major problem on the highways， a problem that is aggravated by increases in motorcycle use；on many roads，bicycles and mopeds are added to the problem．
使用较小的汽车和较大的货车的倾向已经在公路交通中造成了一个大问题，机动车辆的增加更使此问题变的严重。在许多道路上自行车和机动脚踏两用车的使用又使这个问题加重。
2．A majority of accidents are still attributed to ‘human error'，or driver impairment through the use of alcohol or other drugs，even though it is clear that only minor advances can be expected in controlling this problem．
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交通工程专业英语
大多数事故仍是由于“人为过失”造成的,即由于驾驶员因使用酒精或其他药物而受到损伤造成的，尽管在控制这一问题方面的进展不会很大.
3．Although it is economically impractical to eliminate all grade crossings within a brief time period， grade separation is the only positive engineering solution available and should be scheduled over a reasonable period.
尽管从经济角度考虑在短期内消除所有的平交道口是不切合实际的,但修建立体交叉却是解决问题的唯一切实可行的工程措施,并且应当在适当的时期内提上议程。
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交通工程专业英语
Unit 21 Traffic Management
Text
Objectives
Traffic management arose from the need to maximize the capacity of existing highway networks within finite budget and， therefore， with a minimum of new construction. Methods， which were often seen as a quick fix, required innovation solutions and new technical developments。 Many of the techniques devised affected traditional highway engineering and launched imaginative and cost effective junction designs。 Introduction of signal—controlled pedestrian crossings not only improved the safety of pedestrians on busy roads but improved the traffic capacity of roads by not allowing pedestrians to dominate the crossing point.
More recently the emphasis has moved away from simple capacity improvements to accident reduction, demand restraint, public transport priority， environmental improvement and restoring the ability to move around safely and freely on foot and by pedal cycle。 Demand management
There has been a significant shift in attitudes away from supporting unrestricted growth in highway capacity. The potential destruction of towns and cities and the environmental damage to rural areas are not acceptable to a large proportion of the population。 Traffic management has， largely， maximized the capacity of the highway network, yet demand and congestion continue to increase.
Highway authorities accept that they do not have a mandate to provide funds for large amounts of new construction。 It is clear that， for the foreseeable future， resources will not be available to provide for unrestricted growth in private vehicular traffic。 Traffic engineering alone cannot provide for sufficient highway capacity even with limited amount of new construction。
One method of demand management that has received considerable interest and study is congestion charging。 This is where vehicles are surcharged for their use of road space depending on the prevailing levels of congestion. New technology in the form of smart cards and vehicle identification are needed to ensure that the system is practical and fair。 Measures to accommodate foreign or nonlocal vehicles are also needed。 Video image analysis has reached a level of sophistication that can be used for this purpose。 Engineering measures
The traffic engineer has a vast array of measures which can be applied to achieve his objectives。 These objectives include： capacity enhancements； accident reduction； environmental protection and enhancement; servicing of premises and providing access； providing assistance to pedestrians and cyclists; assisting bus or tram operators; providing
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交通工程专业英语
facilities for persons with disabilities; regulating on-street and off—street parking。 The majority of capacity problems occur at road junctions。 In urban areas road junctions are important focal points for pedestrian and cycling activity and are often the site of public transport interchanges. Due to the various conflicting demands it is not surprising that two-thirds of urban traffic accidents occur at road junctions。 Selection of an appropriate junction design for a particular site can be very difficult。 Some designs， such as roundabouts， can significantly reduce the severity of vehicle—vehicle accidents but can prove hazardous for cyclists。 In some instances installation of traffic signals with full pedestrian and cycle facilities and bus priority measures might also reduce the overall traffic-handling capacity。
Careful allocation of road space to separate traffic streams into designated traffic lanes can reduce confusion and limit accidents. Designation of traffic lanes might include special vehicle lanes, such as cycle and bus lanes and dedicated left— or right-turn lanes。
Introduction of banned turns and one—way streets can reduce potential conflicts and accident potential. These measures can be used to implement protected pedestrian or cycle crossings and simplify junction layouts generally. Great care must be exercised when one-way street schemes are being considered as they can result in speeding by drivers who are confident that they will not be opposed by other vehicles。
Point road closures are used to simplify junction and highway layouts and eliminate turning conflicts。 The resulting continuous footway can also improve pedestrian safety and provide space for bus stops, cycle racks, pedestrian crossings, and hard and soft landscaping。 Closure of long sections of road to general traffic can produce pedestrianized shopping streets. Such scheme can be very complex to design and introduce， because facilities for buses, emergency services vehicles， residents/proprietors and service vehicles must be considered。 Carriageway narrowing can be used to limit capacity or vehicle speeds and reduce parking and pedestrian crossing distances。
The key to all successful traffic engineering scheme is that the visual cues provided by the road must give a clear indication to users of who has priority. Junction types
There are many varying detailed junction types， but they can be broken down into five basic types: uncontrolled nonpriority junctions; priority junctions; roundabouts； traffic signals； grade separations。 Road markings
It is not possible to overestimate the importance of road markings as part of the road system。 In a few instances road markings merely emphasize the layout of the highway and guide road users to a safe course of action。 In many cases the whole of the success of a scheme relies upon the visual messages emanating from the road markings。 Traffic signs
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交通工程专业英语
Traffic signs fall into four categories： warning signs; regulatory signs; directional informatory signs； other informatory signs。
Warning signs provide information to road users about hazards such as junctions, changes of direction, carriageway width， gradient， low， opening or humped back bridges， roadworks etc。
Regulatory signs provide a message that must be obeyed， such as stop, give way， banned turn， compulsory turns， no entry, one—way streets， prohibited vehicle types, weight and width restrictions, waiting and loading restrictions, speed restriction etc。
Directional informatory signs provide information about routing and important places of interest， such as railway stations， airports etc。
Other informatory signs provide information about footway and other parking schemes, heritage sites， census points etc。 Traffic signs are often installed in association with road markings.
Notes
1。Traffic management arose from the need to maximize the capacity of existing highway networks within finite budget and, therefore, with a minimum of new construction.
交通管理起源于这样一种需要，那就是在预算有限的情况下，以最少的新建工程项目，最大限度地提高现有道路网的通行能力。
2. More recently the emphasis has moved away from simple capacity improvement to accident reduction demand restraint， public transport priority， environmental improvement and restoring the ability to move around safely on foot and by pedal cycle。
最近(交通管理的)重点已从简单的通行能力改善转移到减少事故、限制需求、公交优先、环境改善和保障步行者及自行车骑行者的安全、自由通行等方面.
3. Closure of long sections of road to general traffic can produce pedestrian ized shopping streets。
从常规交通中封闭一大段路可以形成步行商业街。
4. Regulatory signs provide messages that must be obeyed, such as stop， give way, banned turns， compulsory turns, no entry， one—way streets， prohibited vehicle types, weight and width restrictions, waiting and loading restrictions, speed restriction etc.
禁令标志提供一些必须遵守的信息，例如停车、让路、禁止转弯、强行转弯、禁入、单行线、车种限制、车重和车宽限制、停留及装载限制以及速度限制.
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交通工程专业英语
Unit 22 Traffic Surveillance
Text
Traffic surveillance is an integral and essential part of freeway traffic management systems。 Surveillance entails the status monitoring of traffic conditions and of control system operation as well as the collecting of information for implementing controls and for incident detection。 The surveillance system provides data on the system operating conditions， upon which appropriate decisions and control actions are taken, whose effects on the system operations are then monitored by the surveillance system。 There is thus a closed loop of information, decision， control， and impact。 The concept of surveillance is new. The effectiveness of implemented controls， as reflected by prevailing traffic conditions and the status of control system operation， has always been of interest to traffic engineering agencies。
These aspects of surveillance are common to both urban street and freeway traffic control systems, whose effectiveness is clearly dependent on the reliability and accuracy of the surveillance system， especially in the case of traffic responsive control。 For freeways, however， perhaps the most important aspect of surveillance is the detection and servicing of incidents， which principally contribute to nonrecurring freeway congestion. On the other hand， problems caused by incidents on urban streets are generally less severe than those on freeways， since emergency and repair services， along with alternative routes， are usually more readily available. Thus， the provision of surveillance for incident detection and servicing on urban streets is less common than on freeways. The various methods of surveillance presented in this section are most typically applied to freeways for incident detection and servicing. Each method is thus discussed principally in terms of such a perspective. However， some of these techniques also serve the purpose of measuring traffic performance and control effectiveness, applicable to urban street systems. Such applications are indicated where appropriate。
Incident detection
The earliest traffic surveillance techniques used for incident detection were field observations， periodic studies, police reports， and citizen calls. Today， surveillance for incident detection is carried out through the deployment of a wide variety of methods： ①Electronic surveillance ②Closed—circuit television ③Aerial surveillance
④Emergency motorist call systems ⑤Citizen—band radio ⑥Police and service patrols
Electronic surveillance
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Electronic surveillance for incident detection is accomplished by the real-time computer monitoring of traffic data collected by detectors installed at critical locations。 The measurement of traffic performance and control effectiveness， for urban streets as well as for freeways, can also be carried out by such an installed system。 The discussions of different freeway control strategies in earlier sections of this chapter have indicated the essential manner in which electronic detection is used to implement these strategies. It remains， therefore, to describe how incident detection is accomplished through electronic surveillance。
When a delay-causing incident occurs on the freeway, the capability of the freeway is reduced at the point of occurrence and, if it is reduced to a value less than the prevailing demand， the traffic flow upstream of the incident is also affected。 Most freeway incident detection algorithms involve the determination of changes in certain traffic—flow variables which are believed to be caused by, or correlated with, the occurrence of incidents。 If detected changes in the traffic flow variables are greater than some predetermined values, the occurrence of an incident is indicated. Thus， incidents are detected by logically evaluating the variations in traffic flow characteristics.
An operational system in which this concept is being effectively used is the Los Angeles Freeway Surveillance and Control Project。 In this system, changes in lane occupancy between adjacent detectors are used to sense congestion and indicate the occurrence of an incident。 At the end of each sampling period, a computer calculates the percent difference in occupancy between adjacent detector stations spaced at 1/2—mi （800—m） intervals。 When the relative percent change between the present occupancy and the occupancy of the preceding sample for the downstream detector exceeds a predetermined value, the computer automatically signals an alert. Additional information on traffic conditions immediately upstream of the incident can then be obtained， and judgment decisions are made with regard to what other response is needed： for example， what equipment to dispatch and whether nonelectronic surveillance are required。 The principal advantages of electronic surveillance for incident detection are： it is the only system that provides a continuous networkwide monitoring capability at relatively low costs； and the installed systems can be used for many other tasks, such as the establishment of metering rates for traffic-responsive， ramp-metering systems。 The main disadvantage is that the nature of the incident cannot be determined by the system, so that some follow—up surveillance is required to determine the response needed。 Also, electronic surveillance for incident detection is yet to be tested for a large network， and general incident—detection strategies have not been perfected for this purpose。
Notes
l. The surveillance system provides data on the system operating conditions， upon which appropriate decisions and control actions are taken, whose effects on the system operations are then monitored by the surveillance system。
监视系统提供系统运行条件数据，根据这些数据可以做出正确的决策并采取相应控制措施，它们对系统运行的影响也是受监视系统监视的。
2。 These aspects of surveillance are common to both urban street and freeway traffic control systems, whose effectiveness is clearly dependent on the reliability and accuracy of the surveillance system， especially in the case of traffic responsive control。
对于城市道路与高速公路的交通控制系统来说，监视系统的这些方面是相同的，它们的
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工作效率显然取决于监视系统的可靠性与精确度，尤其是在交通感应控制的情况下. 3。 Each method is thus discussed principally in terms of such a perspective。 However, some of these techniques also serve the purpose of measuring traffic performance and control effectiveness， applicable to urban street systems.
因此，每种方法基本上都根据这一观点来论述.但有些技术在城市道路系统中也可以用来监测交通性能和控制效果。
4。 Electronic surveillance for incident detection is accomplished by the real-time computer monitoring of traffic data collected by detectors installed at critical locations。
用于事故检测的电子监视由实时电脑监控系统来完成，所需的交通数据由安装在关键位置的检测器采集。
5. Most freeway incident detection algorithms involve the determination of changes in certain traffic-flow variables which are believed to be caused by， or correlated with， the occurrence of incidents.
大多数高速公路事故检测运算方法涉及确定某些交通流量的变化，这些变化相信是由事故造成的，或与事故有关。
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