交通工程专业英语

Unit3

I ntroduction

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.

Before leaving home, you check your travel arrangements over tile internet. Often you choose to travel by public transport and you can identify travel times and any interruptions affecting the service. On this occasion, you choose to travel by car as you have an appointment later in the day at one of those oldfashioned business parks that are inaccessible by public transport. There are no incidents recorded on your normal route to work so you do not bother to use your computer route model to select an optimum route for you.

Once in your car, you head for the motorway and select the cruise control, lane support and collision avoidance system, allowing you to concentrate on your favorite radio service. Suddenly, this is intelrupted by the radio traffic-message channel service giving you information about an incident on your route. You are not surprised when, at the next junction, the roadside variable message sign (VMS) corffirms this; motorway messages really are believable now!

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.

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 collision control just to be sure of not scratching the MD' s car next to you.

Using transport telematics

All these information and control services, and many more besides, are discussed in the UK Government' s eonsuhation document. One way of categorising these services is into the following application areas: （1）traffic management and control

（2）tolling and road pricing

（3）road safety and law eifforeement

（4）public transport travel information and ticketing

（5）driver information and guidance

（6）freight and fleet management

（7）vehicle safety

（8）system integration

All these applications are being developed with assistance from research and pilot implementation programmnes in Europe, USA and Japan.

Traffic management and control

Any traffic management and control system needs information on traffic flows, speeds, queues, inci-

dents (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: （1）influencing traveller behaviour, in particular modal choice, route choice and the time at which journeys are made.

（2）reducing the impact of traffic on air quality.

（3）improving priority for buses and LRT vehicles.

（4）providing better and safer facilities for pedestrians, cyclists and other vulnerable road users.

（5）restraining traffic in sensitive areas.

（6）managing 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

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 ehannel, 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 networks 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.

翻译：介绍

交通通讯,也被称为智能交通系统(它的),与应用电子信息和控制,提高运输。一些新的系统已经被实施和速度的加快实施可预期的。用水晶球,我们可以预见到工作的一个典型的旅程如何在10年内可以看。

离开之前回家,你检查你的行程安排在瓷砖的网络。通常情况下,你选择乘公共交通,你可以确定旅行时间,任何干扰影响服务。在这种场合,你选择乘汽车旅行你有预约当天晚些时候在其中的oldfashioned人迹罕至的商业园区由公共交通工具。没有事件记录在正常上班,所以你不愿意去使用你的计算机模型来选择一个最优路径路由。

一旦你的车,你头上的高速公路和选择巡航控制,弄的支持和船舶避碰决策系统,让您专注于你的喜爱的广播服务。突然,这是由无线电traffic-message intelrupted信息渠道服务给你一个事件的路线。你不会感到惊讶,在接下来的时候,路边的可变信息标志(此信息高速公路corffirms),真的是可靠的!

你觉得满意,你有你自己的车内导航系统之前与协调自己的最终目标,你很快就有最好的路线指示,与当地的旅游信息更新的控制中心。

当你靠近你的工作场所,你意识到路边的消息通知你下次的公园和骑马的服务。你选择不理会这些,因为你将需要做出迅速地离开你的约会。然后你核对一下你的旅行卡是清晰地显示里面,你不想被罚款并没有积极的信用城市道路计费系统、停车服务!相同的卡片给你,你的停车场停车;你激活您的视力和碰撞控制只是为了一定不是抓MD的车你旁边。

利用传输通讯

所有这些信息和管理服务,以及许多之外,有了英国政府的eonsuhation文件。这些服务的一种方式是categorising到下面的应用领域。

(1)交通管理和控制

(2)收费和道路计费

(三)道路安全,法律eifforeement

(四)公共交通出行信息和票务

(五)司机信息与指导

(六)运费和车队的管理

(七)车辆的安全,

(八)系统集成,

所有这些应用程序开发与研究,帮助programmnes试点实施,在欧洲、美国和日本。

交通管理和控制

任何交通管理和控制系统需要的信息流量、速度、队列,inci -

凹痕(事故,车辆故障,障碍物)的空气质量和车辆类型、长度和重量。

该信息将利用红外线、收音机、循环、雷达、微波或视觉检测。

此外,公共或私人机构将提供的信息(roadworks、休閒活动策划、展览活动)。

使用这个信息是将取决于目标管理和控制。

网络管理的目标设定为都市地区包括:

(1)影响旅客的行为,尤其是模态的选择、路径选择和的旅程。

(2)减少交通影响的空气质量。

(三)提高公共汽车和轻轨车辆的优先权。

(四)提供更好的和安全设施,骑自行车和行人等脆弱的道路使用者。

(五)约束的交通中敏感部位。

(六)管理需求和拥挤的效率更高。

使用该软件系统包括控制的应用,如又SCATS、地点和运动,。这些都反应系统,控制网络的交通信号实现这些目标。自动识别系统,提供信息给优先权或允许获得一定的车辆。

近期网络管理系统会有相似的目标,但是要使用更多的访问控制的计量和其他方式由斜坡和速度控制和high-occupancy车辆巷治理。区域交通控制中心将会建议司机的事件和可供选择的路线通过由RDS-TMC船民及信号调频无线电广播局部交通信息服务和建议司机。

收费和道路计费

近期高速公路收费和城市道路计费系统提供了另一种方法来开会时,网络管理目标获得额外收入,可以投资于运输。新加坡的电子区定价,TOLLSTAR电子收费,二是自动的智能卡应用实例。

这些系统依靠微波或无线通信的应答机在智能卡介面与检测车辆的汽车牌照使用图像处理的强制执行的目的。

公共交通出行信息和票务

旅游需要信息由旅客在家里或办公室,也在他们的旅程。伦敦的路线,以计算机为基础的服务提供了路由、时间表和信息的公共交通票价都在伦敦通过公众咨询服务。

实时旅游信息在伦敦的地铁倒计时,扩展至包括4000个车站。一个相似的系统叫做秒表是可在南安普顿的ROMANSE项目的一部分,是基于皮克的公共汽车的跟踪系统可以检测汽车使用无线电界标或GPS(全球卫星定位系统),使用卫星来确定地点。

ROMANSE还包括旅行lanner互动询价终端和触摸屏提供旅游信息。

问题可以通过旅行票对旅游者选择一个威慑的公共交通工具。

Smartcard储值票可以提供一票,所有的停车场的一段旅程由不同的运营商。

司机信息与指导

司机信息系统包括RDS-TMC无线数据system-traffic ehannel讯息,初步完成伦敦和巴黎之间在昂宿星项目和在欧洲其它地方在类似的EC-funded项目。也有交通主人使用红外线监控服务来识别拥挤和一内置的视觉图谱屏幕通知司机的阻塞。

司机诱导系统的目的,借此进一步通知司机的路径与导航。人与人之间的控制中心和车辆可以被路边的灯塔或数字蜂窝无线网络基于GSM(全球移动通信系统)在苏格拉底。商业产品包括戴姆勒奔驰的副机长动态路径诱导系统在柏林与斯图加特和完成CARIN菲利普的汽车系统。类似的产品,如VICS先进移动信息服务,通常是在日本。

Unit4Public Transport Priority

2008-12-12 22:13

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:

1to improve the conditions and reliability of bus operations through the introduction of appropriate bus priority measures.

~to alter the traffic balance in favor of buses at those locations where this can be properly justified.

(~to improve conditions for bus passengers at stops and interchanges.

Oto improve road safety generally and, in particular, for pedestrians, cyclists and

people with disabilities.

~to review, where appropriate, hours of operation of waiting and loading restrictions.

(~to establish and implement the coordinated and coherent application of waiting, parking and loading enforcement regimes on bus route corridors.

Oto improve conditions for all mad 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:

~bus lanes and busways

(2_)traffic and parking management measures

Qtraffic signal control ~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

(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 commemial 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: @ Signal rephrasing for passive bus priority

@Selective vehicle detection-active bus priority @ Overlap phases "@ Queue relocation and traffic metering @ 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 ofrices, 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 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.

翻译：设计目标,

公交优先已被看到在整体城市交通的战略目标,不仅包括改善公共汽车(或电车)操作和克制,car-borne通勤更是一种增强环境,为居民、工人和游客。方法必须为所有这些也有明显的目标而成本和执行。

典型的设计目标为公交优先的措施包括:

以上条件和可靠性,提高经营通过引入适当的公交优先的措施。

~来改变这种交通平衡赞成在这些地点的正确的话,这可能会是正当的。

(~改善条件公交乘客在停止和立体交叉。

针对提高道路安全一般,特别是对行人、自行车、残障人士。

哦~,在适当的时候,小时的手术的等待和加载的限制。

(~建立、实施协调和连贯的应用中等待,停车场和加载执法机制在巴士路线走廊。

针对提高条件和frontagers疯狂的用户在巴士路线走廊。

实现这些目标通常包括提高汽车运行和妥协需求的本地企业和居民和行人获得合理的安全、便捷、自行车运动。

公交优先的措施

典型的公交优先措施可分为4种类型:

busways ~、公共交通

(2_)交通和停车场管理措施

Qtraffic信号控制~汽车站的改进。

这些被认为是独立的,但在实践中设计了一个巴士路线走廊将着重从所有这些措施类别。

(1)busways、公共交通

With-flow公交车道较为普遍。他们能够在拥挤的公共汽车来避免队列的道路通过提供一个弄清楚标明签署和执行,在交通管制禁令,禁止使用一般的交通。

Contraflow公交车道,避免迂回路线使汽车,如在一种回转系统,通过允许双向运动在路段上公共汽车。一个连续的主要缺点是它contraflow巴士车道街道访问由车辆,防止如货运车辆,不准使用它。

Busways和bus-only街道提供一个专门的轨迹,用公共汽车

(2)交通和停车场管理措施

这是典型的no-entry,禁止将控制,允许公共汽车(也可能是骑自行车的人)做运动禁止其他车辆。

财务和空间的许可证。一个解决方法是权威的高速公路提供存取路线,使commemial性能下降,提供肩和让居民获得相对的,在豪宅的停车的性质。

(三)交通信号控制

交通信号控制包括:@信号的言论@Selective车辆被动公交优先detection-active公交优先队列中“@ @重叠阶段安置、交通和公共汽车Presignals计量@推进区域。

(四)。公共汽车站的改进

一个主要的原因,在市区巴士延迟和一般的交通是不顾别人的停车场附近公交车站。在公共汽车上有困难进入车站的交通流,随后会合。乘客不得不诉诸行走在汽车上公共汽车。

有时实施等,是不恰当的,因为这加载的限制会阻止合理使用的长度的路肩上由当地居民和企业。一种解决办法就是阻止停车的地方去公共汽车站为乘客提供更容易通过构建登机,包括本地总线滑板的延伸到车道的相对1.0-2.0m有关。

巴士站的定位,通常是由实际问题,如避免银行、邮政ofrices空间,在需要特殊的交货,避免创建视力线为侧道路交通。

公共汽车是一种明显的改善避难所的巴士站,提供保护不受天气。

时间表信息还应具备在公车站在普通静电上市的日程安排时间的汽车到达目的地,达到停,或为实时信息。

一批肩是高边平底弯肩使公共汽车司机来排列他们的车辆精确在公车站。伟大的优点是登机,其后是near-level旅客出入境的汽车,而不需要重新走上道路。

Unit5 Urban Transit Definitions

Urban transit systems are the common carriers of passengers in cities. Urban transit is not a distinct technology, but an operational and institutional concept. It uses highway and railroad engineering extensively, as well as the operations and management methods employed by common carriers in any of the other transportation modes.

This paper is therefore concerned with providing information on the physical and operational characteristics of urban transit specifically. The reader is referred to other knowledge for further details on railroad engineering, motor vehicle characteristics, travel demand and modal choice, planning considerations, and similar material.

After defining important terms used in urban transit, the paper surveys the physical characteristics of such systems (right-of-way, vehicles, routes, stops, and performance), operational procedures, and the economic and management aspects that define the capability of transit and its contribution to urban mobility.

Special words and phrases used in urban transit systems may be defined under the headings of general function, technology, and types of service.

General function definitions

(1)Urban transit (also called nmss transit) is a common carriers service provided for the carriage of passengers and their incidental baggage on established routes and fixed schedules at published rates of fares, and available to all persons wishing to avail themselves of the service.

(2)Paratransit is a service that deviates from the preceding definition in that it may not follow fixed routes or schedules, may not be available to the general public, or both. Examples include taxis, vanpools, club buses, and demand-responsive services.

(3)Charter service is based on contracts between a transit agency and individuals

for occasional or regular hire of vehicles and drivers, is restricted to the use of the contracting party, and follows whatever route and schedule this party desires. Technological definitions

(1)Right-of-way refers to the land used by the transit systems. It may be shared (street transit), semiexclusive (light rail transit, buses, and high-occupancy-vehicles

on reserved lanes), or exclusive (rail rapid transit).

(2)Guideway or infrastructure refers to the right-of-way plus the special improvements required for operations (e.g., tracks, power distribution, control system).

(3)Revenue vehicles are the rolling stock operating on highways or gnideways which furnishes the actual passenger transportation. The term transit unit designates an individually scheduled service, which may be a single vehicle or a train. The following major categories are cornmonly used:

(DVan: A passenger vehicle on an automobile or light truck chassis propelled by an internal combustion engine, with a capacity for 6 to 15 persons.

(~)Minibus A vehicle less that 25ft (7.5m) long, propelled by an internal combustion engine, with a capacity for more than 15 persons.

(~)Transit bus: A vehicle more than 25ft (7.5m) long, usually propelled by a diesel engine.

(_4)Trolley bus: A transit bus propelled by electricity obtained from overhead wires.

(~Articulated bus: A transit bus (diesel or electric) with a permanently attached semitrailer, with full interior passenger circulation.

(~)Streetcar or light rail vehicle (LRV) : An electrically propelled rail vehicle operated singly or in trains on shared or semiexclusive right-of-way.

~

(~Rail transit car: An electrically propelled vehicle usually operated in trains on exclusive right-of- I

way. i (~)Commuter railroad car: A standard railroad passenger car with high-density seating. It may be

self-propelled (by electricity or diesel engines) or designed for haulage by locomotive.

(4)Light rail transit (LRT) refers to rail service at least partly on shared or semiexelusive right-of-

way, designed so that other traffic can mingle safely with the LRT operation where desirext.

(5)Heavy rail transit (HRT) (also called rapid transit in common parlance) refers to rail service on exclusive right-of-way, designed without need to accommodate any other type of traffic.

Service definitions

(1) Local transit is service on streets or other right-of-way making frequent stops and, hence, operating at relatively low speeds, serving adjacent land uses within acceptable walking distances.

(2)Express service is service that does not attempt to serve all land areas through which it passes,but offers faster speeds to a selected number of stops spaced more

widely apart.

(3) Basic service comprises routes that operate all day (although the length of the 'day' may vary from about 14 to 24 h), and at least 5 days/week.

(4)Peak service comprises routes that supplement basic service during peak demand periods only.

(5) Special service comprises irregular routes operated for special events or for seasonal traffic generators.

(6)Short-haul transit refers to service within major activity centers over short routes. Special technology is sometimes used.

翻译：城市交通系统是常见的航空公司的乘客在城市里。城市交通不是一种截然不同的技术,而是一种操作和制度的概念。它使用公路、铁路工程上得到广泛应用,以及运营和管理方法采用常见的航空公司在其他的交通方式。

本文是提供信息的物理特性和经营城市公共交通。读者是指其他知识之详情铁路工程、汽车特点的基础上,对旅游需求和模态的选择、规划考虑,和相似材料。

用于定义城市轨道交通的重要方面,本文调查了此系统的物理特性、车辆、线路(侧,停止和表演)、操作规程、经济和管理方面的能力的定义及其贡献过境城市流动。

特别的词和短语的城市交通系统中使用的标题下可定义的一般功能、技术和服务。

一般函数定义

(1)。城市交通运输网络管理系统(也被称为)是一种常用的航空公司提供的服务的旅客及其行李上建立了路线,附带的时间表,固定费用、出版及提供给所有人希望利用自己的服务。

(2)。Paratransit是一种服务,背离了定义,因为它可以前不遵循固定线路或进度表,不得公开的,或者两者兼有。例子包括出租车、公共汽车、vanpools,俱乐部demand-responsive服务。

(3)。特许服务是基于合约的一家运输公司和个人之间或定期雇佣的偶然车辆和司机、限制使用缔约国,遵循这个政党路线和时间表的欲望。

技术的定义,

(1)。站房用地红线是指土地使用的交通运输系统。它可以共享(街道),semiexclusive(轻便铁路、公共汽车和high-occupancy-vehicles保留车道上),或者独家(轨道快速转关)。

(2)。导轨或基础设施是指侧加上特殊的进步所需要的操作(例如,追踪、配电、控制系统)。

(3)。机车车辆的收入在高速公路上,或gnideways运作提供实际的客运。这个词单位指派一个单独安排运输服务,这可能是一个单一的汽车或火车。下面是cornmonly大类: (DVan:乘用车在汽车和轻型卡车底盘的推动下,内燃机,有能力为6 - 15人。

(~)。一辆巴士,25ft少(750万)长,由内燃机、容量超过十五人。

(~)。交通车辆总线:超过25ft(独立)长,通常被柴油发动机。

(_4)。公共汽车:运输汽车手推车推动电力线路从头顶。

(~表达公共汽车:交通公共汽车(柴油或电)和一个永久附semitrailer内部循环,乘客。

(~)。巴士或轻轨交通工具(轻轨):一个电推进轨道车辆运行在火车上单独地或者共享或semiexclusive让行。~

(~轨道车:一个电动汽车通常在推动的独家right-of列车——我道。我

(~)。通勤火车:一个标准的铁路客车和高密度阀座。这是可能的

推进(用电或柴油发动机)或设计以机车牵引。

(四)。轻轨交通(轻轨)指铁路服务至少部分共享或semiexelusive right-of -

路设计,所以其他交通工具,可以安全的地方desirext轻轨交通运行。

(五)。沉重的轨道交通(HRT)(也叫做快速公交系统工程中常见的说法)是指公路铁路服务,设计不需要独占容纳其他类型的交通。

服务的定义,

(1)当地的运输服务在街上或其他公路使频繁停下,因此,在相对较低的速度运行,相邻土

地用途在可接受的步行距离。

(2)。快递服务是服务,不去尝试来为所有陆地通过传球,但提供更快的速度来选定的间隔更分开。停止

(三)基本服务包括航线操作一整天的长度(虽然日”的不同而不同,约为14到24小时),

至少5天/周。

(四)。服务包括:高峰期间,补充航线服务需求高峰时期基础。

(五)特别的服务包括:不规则的路线进行手术,特殊事件或季节性的交通发电机。

(六)。短途运输服务,主要是指在短期内活动中心的路线。有时是用特殊的技术。

Unit6 Highway Systems and Functional Classifications

Highway Systems and Functional Classifications

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 classiiieation 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 nnn~er 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 dinfinate the functional need for the remaining parts of the flow hierarchy 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 hierarehy is a prominent cause of highway obsolescence. Conflicts and congestion occur at interfaces between public highways and private traffic-generating facilities when the functional transitions are 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 beeomes 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.

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 estal)lished 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 cases intermediate elements may be bypassed.

翻译：系统和分类

高速公路上的分类管理系统,分成不同功能类或几何特征之间的交流是必要的,工程师,管理者和一般公众。不同的分类方案已应用不同目的在不同的农村和城市地区。通过对高速公路设计类型分类的主要基于几何特征(如、高速公路和传统的街道和高速公路)是最有益的人对高速公路位置和设计过程。分类路线编号(如美国,初选的各州,公立中等,县编码系统,是最有利于交通行动。行政分类(如州联邦资助小学、中学、州州立联邦的援助,并公立中等)是用来表示该级政府负责、融资、公路设施。功能分类、分组的高速公路的特征,他们提供的服务为交通规划的目的。综合交通规划、不可或缺的总经济和社会的发展、使用功能分类

作为一种重要的规划工具。classiiieation的出现为主要功能的分组的方法是一致的政策公路载列在本刊物。

功能分类的概念

具有完整功能的设计系统提供了一套截然不同的旅游活动。6辨认阶段包括主要的运动,最旅行的过渡,分布、收集、访问,并终止本协议。例如,假设的公路旅行用的一条高速公路上,那里的主要运动车辆不间断的,高速流。当靠近高速公路的目的地,在高速公路上的车辆减速斜坡,作为过渡的道路。然后进入moderate-speed汽车经销商设施,使他们病理更接近目的地附近的社区。他们下进入收藏家的道路。穿透车辆的道路上,最后进入当地存取提供直接的方法对个人住宅或其他终止。在他们的车停在目的地在恰当的终端设备。

这六个阶段的一个典型的行程是由另一家工厂专门设计用于其功能。由于运动等级是基于交通流量总额,高速公路旅行是最高层次的运动中,紧随其后的是动脉旅行代理商的运动中,在更高层次上的收藏家和当地比旅行路线。访问

尽管许多旅游可分为:所有的六个可辨认的阶段,中级设施不总是需要。完整的层次关系,尤其是对流通设施条件下的低密度郊区的发展,在流量累积在连续的元素。然而,有时就需要减少nnn ~呃部件的链条。例如,一个大的单一交通发电机可以填补一个或多个车道高速公路的在一定期限内。在这种情况下,是导致斜坡上的一条高速公路上的交通设施的不混already-concentrated不必要的动脉硬化和额外的车辆的流量。这删除中级设施不dinfinate功能需要的其余部分的功能设计流量等级或部件,尽管它可能会改变他们的物理特性。秩序的运动仍然辨认。

失败的认识和容纳通过合理设计的各阶段的旅行是一个突出的原因hierarehy公路被淘汰。冲突和阻塞发生在高速公路之间的接口和私人traffic-generating设施功能转换时的不足。实例,直接从商业车道高速动脉变成一个相对不停车走道中间为过渡减速和动脉分布,或者更严重的是,高速公路上坡道,直接进入或从大型发电机等主要交通购物中心。

接受能力不足的经销商或内部循环不足动脉内吸收的危险的交通流量可以创建备份到高速公路。成功的内部设计提供设施容纳所有的终端停车设施将缓解这种情况。

在高速公路上导致了大量的交通发电机、减速从快速运动在高速公路上发生了出口的斜坡。分配到各种各样的停车区域则是由基本分布式道路或车道在停车场设施。这些道路或车道取代经销商动脉功能。Collector-type车道公路或者在停车设施可以提供的个人进入流量停车位终端,然后beeomes相当于一个访问街。因此,主要功能的分层运动系统是显而易见的。它可以指出各功能类别也是相关的一系列车辆的速度。

同样的原理的设计也有相关的码头设施,毗邻经销商或病理。这个装置的功能设计,包括各运动阶段的内部循环的终端设计提供了秩序的运动。设计的必要性,并对各阶段的不同层次的运动的大小与交通发电机。为相对较小的发电机,两个或两个以上的阶段,可以停放在相同的内部设施。对于大流量发电机,每一个动作阶段必须有一个单独的功能设施。

24?定设计组件,习惯车辆由公共街道的不同功能分类可以进行比较。体积在内部设施可能与相应的范围在公用街道上。这些卷宗不得直接可比性,在尽可能多的物理空间可在一个私人的设施都是小的标准操作一定是截然不同的。然而,同样的原则的专业化和运动的流动层次,可以适用。进一步的例子可以证明如何原则有关运动的层次划分的逻辑系统交通产生的强度。在最高水平的交通产生一个发电机充满整个公路、街道、中级公开这个条件不能插入的发电机和高速公路之间,所以各运动阶段必须对内与适当的设计特点。在接下来的一个交通流量一代发电机可以填补一个高速公路,然后适当建造一条高速公路斜坡专用的发电机不介入公共的街道。在更小的体积变得理想相结合,对来自几个发电机和额外的交通流量的流量之前到达高速路入口的斜坡。执行这个函数的道路将成为收藏家设施、积累这些小流到交通流量,将填补高速公路上斜坡。

类似的原则可以应用在经销商动脉的服务水平。如果一个给定的交通发电机够大的话,那是一个十字路口,发电机车道是合乎情理的。在其他情况下,一个中间收藏家街应结合小流量体积,直到他们保证了交汇点经销商。同一理论可以应用的标准为直接存取收集器的街道。一个中等大小的交通发电机通常可以作为一个直接的联系,而中间存取街收集器;然而,在一

个地区的一个地方存取街独栋住宅的交通应装配在一群住宅和引导它在收集器的街道在单一点的访问。在实践中,直接进入病理和收藏家们必须提供商业和住宅性能,特别是在薇思德)建立起了街道。

总之,每个元素的功能层次可作为收集设施为更高的元素,但是一个元素必须仅出现在中间的收藏是必要的,以满足间距和交通流量的要求更高的设施。通过定义间距和体积所需的系统,它是可能的元素的测定,在什么情况下是必要的,在什么情况下,系统可以忽略。

Unit7 Economics and Transportation Engineering

An economic analysis should not be carried out as an afterthought. It should be used as part of a continuous process, starting with the objectives of the proposed trarrsportation project (can these objectives be satisfied in any other way?), running through the entire planning and design process, and only ending, as a final summing up, with the overall evaluation. It should consider the following questions: (_T)Project identification. Which projects or policies should be considered as possible solutions to a particular transport need?

(~)Establishing rough priorities. Which projects and policies should be considered in detail?

(~)Detailed evaluation. Which costs and benefits are relevant to the evaluation, how should they be measured, and how can they best be presented as an index of priority?

(~)Project selection. Should this project be selected, should it be rejected, or should it be postported?

Economics is often overlooked as an aid to transportation planning and design. Yet any transportation engineering problem involves a whole series of essentially economic decisions. In the area of design, for example, the transportation engineer must choose materials, select an overall design concept, and then combine the component parts of the scheme into an effective, and economical, whole. A river crossing could thus beby ferry beat, causeway, or bridge. In the latter case it could be in steel, concrete, or timber. It could be suspended, arched, or simply supported. What should the engineer choose?

The range of choice is not usually as large as this. Some solutions will be physically infeasible (e.

g., by lack of suitable foundations for an arched bridge), but important choices will remain. In the absence of a rigorous economic analysis, the designer may make these choices on the basis of:

(1)Experience, which may or may not cover an adequate range of options.

(2)Preconceptions as to what is desirable (e. g., one solution uses less material).

(3)An innate view of mathematical or structural elegance (e. g., an arch is a more elegant structural form).

Economics avoids the need for these arbitrary rules by providing a tangible criterion-cost-for choosing between alternative solutions. In many cases this can be

done quite simply by drawing envelopes of cost curves of, for example, steel girder bridges versus reinforced concrete bridges versus prestressed concrete bridges. By plotting cost (y) against span length (x) the engineer can choose which type is most economic over a given range of span lengths.

In practice, the engineer does not usually carry the economic analysis to this level of detail, although curves like this commonly form part of the standard highway design repertoire. It is more a question of the economic attitude of mind that asks: Is this the only possible solution, and if not, is there a better one? It is this general principle which eventually ensures that the final design is the most economical and the one which, if justified in aggregate terms, offers best value for money. Economic efficiency and distribution

Economics is not concerned solely with the optimum allocation of resources, hut with wider questions of equity and the distribution of costs and benefits among individuals, regions, etc. It is thus concerned with the question: who does what, to whom, and at whose expense? In a ~nse this concern complements the intertemporal considerations noted above. A dollar to one person is not necessarily worth the same amount to another. Since economies assumes that marginal values decline as income increases, interpersonal differences in income may thus affect any overall measure of consumer benefit.

Questions of distribution nevertheless go beyond mere differences in income. Institutional constraints usually prevent beneficiaries, defined in the broadest sense, from compensating people who are adversely affected. It is therefore often appropriate to separate the impact of a transport improvement into its effect on different interest groups, in addition to its effect on different income groups.

翻译：经济分析不应该进行一勺面糊。它应该是作为一个连续的过程,从客观的提议trarrsportation项目(可以实现这些目标被满意的任何其他方式?),贯穿整个规划和设计过程,并只结束,最后总结,以综合评价。它应该考虑以下问题:

(_T)。项目鉴定。哪些项目或政策应被视为未解的问题的可能解决特定运输需要吗?

(~)。建立粗糙的优先权。哪些项目和政策应考虑的细节吗?

(~)。详细的评估。相关的成本与效益的评价,应该如何衡量,他们如何才能最好被看作一个指数的优先级吗?

(~)。项目的选择。该项目被选中,应该被拒之门外,应该还是postported吗?

经济学是经常被忽视的帮助交通规划和设计。然而任何交通工程问题涉及到整个系列的本质上的经济决策。在设计领域,例如,交通工程师必须选择材料,选择了一个整体设计概念,然后把部件成一种有效的方案,经济、整体。一条河穿越能因此beby渡轮击败,堤,或桥。后者的例子中,它可能在钢铁、混凝土、或木材。它能暂停,拱型,或简单地支撑着。应该如何选择?工程师,

这个范围的选择通常不一样大。一些方案将身体上不可行(e)。

通过分析[j].缺乏合适的基础,为一个拱形桥),但最重要的选择。在缺乏严格的经济分析,设计人员做出这些选择的基础上。

(1)。经验,这也许是,也许不是一个适当的选择范围。

(2)。什么是一个理想的偏见(如一个解决方案使用较少的资料)。

(3)。一个天生的数学或结构优雅(如一道拱门是一种更优雅的结构形式)。

避免这些经济规则提供了一种切实任意criterion-cost-for之间的选择可能的解决方案。在很多情况下,这可以很简单地用信封的成本曲线,为例,对钢板梁桥的钢筋混凝土桥梁和预应力混凝土桥梁。通过对成本(y轴)的跨度(x)工程师可以选择何种类型是最经济在给定范围的跨度的长度。

在实践中,工程师通常不会把经济分析,这个水平的细节,但这样的曲线的标准的一般形式的公路设计套路。它更是一个问题的经济的态度,问:这是唯一可能的解决方案,如果没有,有较好的吗?这是一般的原则,最终保证最终的设计是最经济的总体上,如果合理条件,提供最优惠。

经济效率和分布

经济学不是只优化资源配置,但有更大的股份和分配问题的成本和收益的个体之间、区域等。它是如此关心这个问题:谁做什么,谁去,在其费用吗?这个问题在~了无跨考虑上面提到的补充。一美元的人不一定是值得等量转到另一所学校。从经济假设的边际价值下降随着收入的增加,人与人之间的差异,从而影响收入消费者利益的任何总体衡量。

不过超出分配问题,仅仅在收入差异。通常的制度约束,在预防受益人,从广义的补偿那些负面影响。因此经常适当分离的影响,其影响交通改进成不同利益群体,除了它的影响不同收入阶层。

Unit8 Sight Distance

The ability to see ahead is of the utmost important in the safe and efficient operation of a vehicle on a highway. On a railroad, trains are confined to a fixed path, yet a block signal system and trained operators are necessary for safe operation. On the other hand, the path and speed of motor vehicles on highways and streets are subject to the control of drivers whose ability, training, and experience are quite varied. For safety on highways the designers must provide sight distance of sufficient length that drivers can control the operation of their vehicles to avoid striking an unexpected object on the traveled way. Certain two-lane highways should also have sufficient sight distance to enable drivers to occupy the opposing traffic lane without hazard. Two-lane rural highways should generally provide such passing sight distance at frequent intervals and for substantial portions of their length. Conversely, it normally is of little practical value to provide passing sight distance on two-lane urban streets or arterials. The length and interval of passing sight distance should compatible with the criteria established in the chapter pertaining to that specific highway or street classification.

Sight distance is discussed in four steps: the distances required for stopping, applicable on all highways; the distances required for the passing of overtaken vehicles, applicable only on two-lane highways; the distances needed for decisions at complex locations; and the criteria for measuring these distances for use in design. Stopping sight distance

Sight distance is the length of roadway ahead visible to the driver. The minimum sight distance available on a roadway should be sufficiently long to enable a vehicle traveling at or near the design speed to stop before reaching a stationary object in its path. Although greater length is desirable, sight distance at every point along the highway should be at least that required for a below average operator or vehicle to stop in this distance.

Stopping sight distance is the sum of two distances: the distance traversed hy the

vehicle from the instant the driver sights an object necessitating a stop to the instant the brakes are applied and the distance required to stop the vehicle from the brake application begins. These are referred to as brakes reaction distance and braking distance, respectively.

Design sight distance

Stopping sight distances are usually sufficient to allow reasonably competent and alert drivers to come to a hurried stop under ordinary circumstances. However, these distances are often inadequate when drivers must make complex or instantaneous decisions, when information is difficult to perceive, or when unexpected or unusual maneuvers are required. Limiting sight distances to those provided for stopping may also preclude drivers from performing evasive maneuver, which are often less hazardous and otherwise preferable to stopping. Stopping sight distances may not provide sufficient visibility distances for drivers to corroborate advance warnings and to perform the necessary maneuvers. It is evident that there are many locations where it would be prudent to provide longer sight distances. In these circumstances, decision sight distance provides the greater length that drivers need. "

Decision sight distance is the distance required for a driver to detect an unexpected or otherwise difficuh-to-perceive information source or hazard in a roadway environment that may be visually cluttered, recognize the hazard or its threat potential, select an appropriate speed and path, and initiate and complete the required safety maneuver safely and efficiently. Because decision sight distance gives drivers additional margin for error and affords them sufficient length to maneuver their vehicles at the same or reduced speed rather than to just stop, its values are substantially greater than stopping sight distance.

Passing sight distance for two-lane highways

Most roads and numerous streets are considered to qualify as two-lane two-way highways on which vehicles frequently overtake slower 'moving vehicles, the passing of which must be accomplished on lanes regularly used by opposing traffic. If passing is to be accomplished with safety, the driver should be able to see a sufficient distance ahead, clear of traffic, to complete the passing maneuver without cutting off the passed vehicle in advance of meeting an opposing vehicle appearing during the maneuver. When required, a driver can return to the right lane without passing if he sees opposing traffic is too close when the maneuver is only partially completed. Many passings are accomplished without the driver seeing a safe passing section ahead, but design based such maneuvers does not have the desired factor of safety. Because many cautious drivers would not attempt to pass under such conditions, design on this basis would reduce the usefulness of the highway.

Passing sight distance for use in design should be determined on the basis of the length needed to safely complete normal passing maneuvers. While there may be occasions to consider multiple passings, where two or more vehicles pass or are passed, it is not practical to assume such conditions in developing minimum design criteria. Instead, sight distance is determined for a single vehicle passing a single vehicle. Longer sight distances occur in design and these locations can accommodate

an occasional multiple passing.

Sight distance for multilane highways

It is not necessary to consider passing sight distance on highways or streets that have two or more traffic lanes in each direction of travel. Passing maneuvers on muhilane roadways are expected to occur within the limits of each one-way traveled way. Thus passing maneuvers that require crossing the center-line of four-lane undivided roadways or crossing the median of four-lane divided roadways are reckless and should be prohibited.

翻译：能够看见前方至关重要的安全、高效运行的汽车在高速公路上。在铁路、车只局限于一个固定的路径,然而闭塞信号系统和训练有素的操作是必要的安全运行。另一方面,道路和高速公路上的车辆和街道是受控制的能力的司机、培训和经验相当丰富多彩。在高速公路上的安全距离的设计师必须提供眼前有足够的长度,司机就可以控制他们的交通工具的操作,避免引人注目的意想不到的东西。走某些车道公路也应该有足够的距离,使得驾驶员看到占领对方没有危害车道。双线农村公路应该通常提供这种传球眼前间隔距离和可观部分的长度。相反,它通常是很小的实用价值,在车道上提供经过眼前的城市街道或病理。这个长度和间隔的距离应符合《视力标准建立在章节说明,具体的高速公路或街的分类。

讨论了眼前的距离的四步:距离要求停止,适用于所有高速公路上的距离,需要通过取代车辆,适用于车道高速公路,只需要决定在复杂的距离;以及标准测量距离用这些设计。

停止眼前的距离

眼前的长度,距离是看得见的司机前方道路。眼前的最小距离可在巷道应该足够长,使车辆行驶或接近设计速度在到达一个静止不动的物体上。虽然更大的长度是可取的,看到的每一点距离沿公路应该至少需要一个低于平均算子或汽车停在这段距离。

停止眼前的距离是两个距离:距离车辆穿越hy的即时司机景点急需一个物体的即时刹车和应用要求停止车辆的制动应用开始。这些被称为制动器制动距离的反应距离和分别。

设计眼前的距离

停止眼前足以让距离通常是合理的主管和警觉的驱动来匆忙阻止在通常情况下。然而,这些距离时,司机必须经常是不适当的复杂决策时,或瞬间信息很难察觉到,或者当意想不到的或不寻常的演习是必需的。眼前的距离限制为阻止也可能阻止驱动执行回避机动,这通常都是可取的,减少有害,否则停下来。停止眼前可能不会提供足够的距离,能见度距离预先警告驾驶员和履行居住的必要的行动。很明显,有很多位置最好提供较长的眼前的距离。在这种情况下,决策提供了更大的长度,眼前的距离驾驶者。"

决定眼前所需的距离,是一个驱动检测difficuh-to-perceive意外或其他信息来源或危险的环境中,在巷道可以直观认识危险或混乱,其潜在的威胁,选择合适的速度和路径,并开始和完成必要的安全机动安全有效。因为决定给司机看距离误差和提供额外充分调动他们的车辆长度相同或减慢速度,而不是只停,其值大于停下来看实质上的距离。

通过对双线高速公路的视线距离

大多数道路和众多的街道都被认为符合车道公路上的车辆频繁的双向的移动中的车辆,超越慢的车道上,必须做到定期使用由对方的交通。如果传递与安全完成,驾驶员应能看到有足够的距离,清晰的交通,完成了没有切断传球机动车辆的会议提前了一个反对车辆出现在此次演习。当需要时,一个驱动可以回到右线车道而过,如果他看到对方的交通太近,此次演习的只是完成了一部分。许多passings是没有司机看见一个安全的传球,但是部分设计这种演习不会产生预期的安全系数的。因为很多谨慎的司机不会试图通过在这样的条件下,在此基础上,设计将减少有用的高速公路。

通过使用视线距离应确定设计的基础上完成的长度必须经过安全正常演习。虽然可以考虑多passings场合,在两个或更多的车辆,它是通过或不实际承担这样的情况在发展中最小的设计准则。相反,视觉距离确定一个车辆通过单一的汽车。再看发生在距离设计和这些地点可容纳偶尔多传球。

1497906多公路的视距

这是没有必要考虑把视线上高速公路、街道,距离有两个或两个以上的车道每个方向的旅行。通过对muhilane巷道演习将发生的范围内旅行方式各单。因此,需要经过演习中不可跨越齿轮或穿过街区的路面铺筑是四分位鲁莽和应被禁止。