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金镛交通工程专业英语

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2020-12-29 19:14
tags:seriousness

估算-theranos

2020年12月29日发(作者:严怪愚)
原文地址:交通工程专业考研学校排名作者:麦田守望者


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
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原文地址:交通工程专业考研学校排名作者:麦田守望者
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 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< br>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。
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原文地址:交通工程专业考研学校排名作者:麦田守望者
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
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原文地址:交通工程专业考研学校排名作者:麦田守望者
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。
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
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原文地址:交通工程专业考研学校排名作者:麦田守望者
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
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
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原文地址:交通工程专业考研学校排名作者:麦田守望者
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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原文地址:交通工程专业考研学校排名作者:麦田守望者
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。< br>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< br>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
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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
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
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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.
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Tolling and road pricing
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
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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。
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,
spee ds,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
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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.
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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.
(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
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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.
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Passel kerbs are high-sided curved kerbs which allow bus drivers to align their vehicles
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
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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 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
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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.
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.
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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
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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.
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
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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
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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 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 14 mi of every residence would be a standard.
To explain and develop land usetravel relationships, four steps of trip generation, trip
distribution, modal split, and traffic assignment are typically followed.
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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 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
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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
volumecapacity 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
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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
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
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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 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.
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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:
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( 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 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.
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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。
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
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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
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
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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. 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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原文地址:交通工程专业考研学校排名作者:麦田守望者
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
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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
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
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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, residentsproprietors 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
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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
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
c 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
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原文地址:交通工程专业考研学校排名作者:麦田守望者
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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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
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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

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.
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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 12-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
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原文地址:交通工程专业考研学校排名作者:麦田守望者
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
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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