《交通工程学》课程教学资源（书籍文献）Traffic Engineering（3rd Edition）.pdf_P26-P30

1.3 HIGHWAY LEGISLATION AND HISTORY IN THE UNITED STATES 11 Federal-Aid Highway Act of 1956 The authorjzation and appropriation of funds for the implementation of the National System of Interstate and Defense Highways occurred in 1956. The act also set the federal share of the cost of the Interstate System at 90%, the first major change in funding formulas since 1916. Because of the major impact on the amounts of federal furtds to be spent, the act also created the Highway Trust Fund and enacted a series of road-user taxes to provide it with revenues. These taxes included excise taxes on motor fuels, vehicle purchases, motor oil, and replacement parts. Most of these taxes, except for the federal fuel tax, were dropped during the Nixon Administration. The monies housed in the Highway Trust Fund may be disbursed only for purposes authorized by the current federal-aid highway act. Federal-Aid Highway Act of 1970 Also known as the Highway Safety Act of 1970, this legislation increased the federal subsidy of non-Interstate highway projects to 70% and required all states to implement highway safety agencies and programs. Federal-Ai(d Highway Act of 1983 This act contained the “Interstate trade-in” provision that allows states to “trade in” federal-aid funds designated for urban Interstate projects for alternative transit systems. This historic provision was the first to allow road-user taxes to be used to pay for public transit improvements. ISTEA and TEA-21 The single largest overhaul of federal-aid highway programs occurred with the passage of the Intermodal Surface Transportation Efficiency Act (ISTEA) in 1991 and its successor, the Transportation Equity Act for the 21st Century (TEA-21) in 1998. Most importantly, these acts combined federal-aid programs for all modes of transportation and greatly liberalized the: ability of state and local governments to make decisions on modal allocations. Key provisions of ISTEA included: 1. Greatly increased local options in the use of federal-aid transportation funds. 2. Increased the importance and funding to Metropolitan Planning Organizations (MPOs) and required that each state maintain a state transportation improvement plan (STIP). 3. Tied federal-aid transportation funding to compliance with the Clean Air Act and its amendments. 4. Authorized $38 billion for a 155,000-mile National Highway System. 5. Authorized an additional $7.2 million to complete the Interstate System and $17 billion to maintain it as part of the National Highway System. 6. Extended 90% federal funding of Interstateeligible projects. 7. Combined all other federal-aid systems into a single surface transportation system with 80% federal funding. 8. Allowed (for the first time) the use of federalaid funds in the construction of toll roads. TEA-21 followed in kind, increasing funding levels, further liberalizing local options for allocation of funds, further encouraging intermodality and integration of transportation systems, and continuing the link between compliance with clean-air standards and federal transportation funding. The creation of the National Highway System answered a key question that had been debated for years: what comes after the Interstate System? The new, expanded NHS is not limited to freeway facilities and is over three times the size of the Interstate System, which becomes part of the NHS. 1.3.3 The National System of Interstate and Defense Highways The “Interstate System” has been described as the largest public works project in the history of mankmd. In 1919, a young army officer, Dwight Eisenhower, was tasked with moving a complete battalion of troops and military equipment from coast to coast on the nation’s highways to determine their utility for such movements in a time of potential war. The trip took months and left

12 CHAPTER 1 INTRODUCTION TO TRAFFIC ENGINEERING the young officer with a keen appreciation for the need to develop a national roadway system. It was no accident that the Interstate System was initiated in the administration of President Dwight Eisenhower, nor that the system now bears his name. After the end of World War 11, the nation entered a period of sustained prosperity. One of the principal signs of that prosperity was the great increase in auto ownershp along with the expanding desire of owners to use their cars for daily commuting and for recreational tsavel. Motorists groups, such as the American Automobile Association (AAA), were formed and began substantial lobbying efforts to expand the nation’s highway systems. At the same time, the over-the-road trucking industry was making major inroads against the previous rail monopoly on intercity freight haulage. Truckers also lobbied strongly for improved highway systems. These substantial pressures led to the inauguration of the Interstate System in 1956. The System Concept Authorized in 1944 and implemented in 1956, the National System of Interstate and Defense Highways is a 42,500- mile national system of multilane, limited-access facilities. The system was designed to connect all standard metropolitan statistical areas (SMSAs) with 50,000 or greater population with a continuous system of limited-access facilities. The allocation of 90% of the cost of the system to the federal government was justified on the basis of the potential military use of the system in wartime. System Characteristics Key characteristics of the Interstate System include the following: 1. All highways have at least two lanes for the exclusive use of traffic in each direction. 2. All highways have full control of access. 3. The system must form a closed loop: all Interstate highways must begin and end at a junction with another Interstate highway. 4. North-south routes have odd two-digit numbers (e.g., 1-95). 5. East-west routes have even two-digit numbers (e.g., 1-80). Figure 1.4: A Map of the Interstate System 6. Interstate routes serving as bypass loops or acting as a connector to a primary Interstate facility have three-digit route numbers, with the last two digits indicating the primary route. A map of the Interstate System is shown in Figure 1.4. Status and Costs By 1994, the system was 99.4% complete. Most of the unfinished sections were not expected to ever be completed for a variety of reasons. The total cost of the system was approximately $125 billion. The impact of the Interstate System on the nation cannot be understated. The system facilitated and enabled the rapid suburbanization of the United States by providing a means for workers to commute from suburban homes to urban jobs. The economy of urban centers suffered as shoppers moved in droves from traditional central business districts (CBDs) to suburban malls. The system also had serious negative impacts on some of the environs through which it was built. Following the traditional theory of benefit-cost, urban sections were often built through the low-income parts of communities where land was the cheapest. The massive Interstate highway facilities created physical barriers, partitioning many communities, displacing residents, and separating others from their schools, churches, and

1.4 ELEMENTS OFTRAFFIC ENGINEERING 13 local shop .SoeidlumrcTesuledinseveal on measures of performance cations to the public hearing n ocess and in the ability of letter grades,fromA to F,describing how well a facility local oppoinents to legally stop many urban highway proje very g Between 1944 and 1956,a national debate ry of highwa facilities must be deter into and out of urban areas,or whether all Interstate fa- Faciliny design involves traffic engineers in the cilities should terminate in ring roads built around urban functic option (including engineers er se, ways In b uld le should hav t was that mos fthe roa istics of their facilitics users who were paying for the system through their road Traffic control is a central function of traffic engi served.Ih neers ar nvolves the esta latter view prevai dicted rapid growth o of tra n to urban conges me a reality and signals Traffic operations involves measures that influence 1.4 Elements of Traffic Engineering overall operation of traffic acilitics,such as onc-way curb management,and There are a number of key elements of trafficengineering (TSM)in 1.Traffic studies and characteristics volves virtually all aspects of traffic engineering in a 2.Peirformance evaluation ncapacity and operations aspects o high -occupancy ven 3.Facility design iowye nd an Intelligent tran 5.Traffic operations portation systems (ITS)refers to the application of moder telecommunications technol- 6.Transportation systems management 7.Integration of intelligent transportation system ogy to the operation and c rol of transportation sys technologies Suc auto ca h nway. tems in-vehicle gps and mapping s stems、.automated Traffic studies and characteristics involve meas enforcement of traffic lights and speed laws,smart con- ing and quantif ing va ous aspect ol way traffi trol devices,and other s is a rapidly emerging fam not lin ed to)traf of tec fic volumes and demands,speed and travel time,delay portation professionals gather information and control accidents,origins and destinations,modal use,and other facilities While the technology continues to expand.o will grapple with the s big brother”is traffic engineers can rate the operating characteris sue his tov terial ed to all of thes tics of individua facilities and facilitie components of the broad and complex profession of as a whole in relative terms.Such evaluation relies traffic engineering

1.4 ELEMENTS OF TWFIC ENGINEERING 13 local shops. Social unrest resulted in several parts of the country, which eventually resulted in important modifications to the public hearing process and in the ability of local oppoinents to legally stop many urban highway projects. Between 1944 and 1956, a national debate was waged over whether the Interstate System should be built into and out of urban areas, or whether all Interstate facilities should terminate in ring roads built around urban areas. Proponents of the ring-road option (including Robert Moses) argued that building these roadways into and out of cities would lead to massive urban congestion. On the other side, the argument was that most of the road users who were paying for the system through their road user taxes lived in urban areas and should be served. The latter view prevailed, but the predicted rapid growth of urban congestion also became a reality. 1.4 Elements of Traffic Engineering There are a number of key elements of traffic engineering: 1. 2. 3. 4. 5. 6. 7. Traffic studies and characteristics Peirformance evaluation Facility design Traffic control Traffic operations Transportation systems management Integration of intelligent transportation system technologies TrafJic studies and characteristics involve measuring and quantifying various aspect of highway traffk. Studies focus on data collection and analysis that is used to characterize traffic, including (but not limited to) traffic volumes and demands, speed and travel time, delay, accidents, origins and destinations, modal use, and other variables. Perfor.mance evaluation is a means by which traffic engineers can rate the operating characteristics of individual sections of facilities and facilities as a whole in relative terms. Such evaluation relies on measures of performance quality and is often stated in terms of “levels of service.” Levels of service are letter grades, from A to F, describing how well a facility is operating using specified performance criteria. Like grades in a course, A is very good, while F connotes failure (on some level). As part of performance evaluation, the capacity of highway facilities must be determined. Facility design involves traffic engineers in the functional and geometric design of highways and other traffic facilities. Traffic engineers, per se, are not involved in the structural design of highway facilities but should have some appreciation for structural characteristics of their facilities. Trafic control is a central function of traffic engineers and involves the establishment of traffic regulations and their communication to the driver through the use of traffic control devices, such as signs, markings, and signals. Trafic operations involves measures that influence overall operation of traffic facilities, such as one-way street systems, transit operations, curb management, and surveillance and network control systems. Transportation systems management (TSM) involves virtually all aspects of traffic engineering in a focus on optimizing system capacity and operations. Specific aspects of TSM include high-occupancy vehicle priority systems, car-pooling programs, pricing strategies to manage demand, and similar functions. Intelligent transportation systems (ITS) refers to the application of modern telecommunications technology to the operation and control of transportation systems. Such systems include automated highways, automated toll-collection systems, vehicle-tracking systems, in-vehicle GPS and mapping systems, automated enforcement of traffic lights and speed laws, smart control devices, and others. This is a rapidly emerging family of technologies with the potential to radically alter the way we travel as well as the way in which transportation professionals gather information and control facilities. While the technology continues to expand, society will grapple with the substantial “big brother” issues that such systems invariably create. This text contains material related to all of these components of the broad and complex profession of traffic engineering

14 CHAPTER I INTRODUCTION TO TRAFFIC ENGINEERING 1.5 Modern Problems for the Traffic as well as the diversion of traffic to alterate routes re. Engineer ation fa cilities has come to the fore.The creation of facilities and We live in a complex and rapidly developing world. Consequently,the problems that traffic engineers are in- volved in evolve rapidly gcstion has for many jor pu ble t The list goes on and on The point is that traffic en. ns thr exnansion of canacity traffic engineers therefore are in- gineers cannot expect to practice their profession only in volved in the development of programs and strategies to e re y tO manage demand in both time an d space and to discour ngineer must any how many vehicles andlor peonle can he allowed to enter congested areas within designated time periods? 1.6 Standard References numb Growth mar for the traffic Enaineer e of ve ion that t In order to remain un to date and a transportation e quality of traffic servic her such development will be disall membership and participation in professional organiza- ed or the devel oper will be highw way and tramt h nomic times.When the economy is sluggish.the issue include the Institute of Transportation Eng ITE).the Transportation Research Board (TRB).the desire to Group of the American Soc encourage development as a ngineers facilities als causes uniaue problems The entire Interstate Svstem has been aging.and many of its facilities have required of the National Academy of Engineering and is a major major reconstruction efforts.Part of the problem is tha ction of nterst receives 0 enginee ng pr red to in the chap facility is nrimarily the sponsibility of state and local most of which will be ref governments.Deferring routine maintenance on these fa of this text.Major references include struction efforts has Traffic Engineering Handbook polic ntial Uniform Vehicle Code and Model Traffic Ordi nance /2 not involved in the initial construction of these facilities Manual on Uniform Traffic Control Devices [3] maintaining traffic.It is easier to ouild a new dedicated right- 000 sues of long-te and short-ter construction det

14 CHAPTER 1 INTRODUCTION TO TRAFFIC ENGINEERING 1.5 Modern Problems for the Traffic Engineer We live in a complex and rapidly developing world. Consequently, the problems that traffic engineers are involved in evolve rapidly. Urban congestion has been a major issue for many years. Given the transportation demand cycle, it is not always possible to solve congestion problems through expansion of capacity. Traffic engineers therefore are involved in the development of programs and strategies to manage demand in both time and space and to discourage growth where necessary. A real question is not “how much capacity is needed to handle demand?” but rather, “how many vehicles and/or people can be allowed to enter congested areas within designated time periods?’ Growth management is a major current issue. A number of states have legislation that ties development permits to level-of-service impacts on the highway and transportation system. Where development will cause substantial deterioration in the quality of traffic service, either such development will be disallowed or the developer will be responsible for general highway and traffic improvements that mitigate these negative impacts. Such policies are more easily dealt with in good economic times. When the economy is sluggish, the issue will often be a clash between the desire to reduce congestion and the desire to encourage development as a means of increasing the tax base. Reconstruction of existing highway facilities also causes unique problems. The entire Interstate System has been aging, and many of its facilities have required major reconstruction efforts. Part of the problem is that reconstruction of Interstate facilities receives the 90% federal subsidy, while routine maintenance on the same facility is primarily the responsibility of state and local governments. Deferring routine maintenance on these facilities in favor of major reconstruction efforts has resulted from federal funding policies over the years. Major reconstruction efforts have a substantial major burden not involved in the initial construction of these facilities: maintaining traffic. It is easier to build a new facility in a dedicated right-of-way than to rebuild it while continuing to serve 100,000 or more vehicles per day. Thus, issues of long-term and short-term construction detours as well as the diversion of traffic to alternate routes require major planning by traffic engineers. Recently, the issue of security of transportation facilities has come to the fore. The creation of facilities and processes for random and systematic inspection of trucks and other vehicles at critical locations is a major challenge, as is securing major public transportation systems such as railroads, airports, and rapid transit systems. The list goes on and on. The point is that traffic engineers cannot expect to practice their profession only in traditional ways on traditional projects. Like any professional, the traffic engineer must be ready to face current problems and to play an important role in any situation that involves transportation and/or traffic systems. 1.6 Standard References for the Traffic Engineer In order to remain up to date and aware, the traffic engineer must keep up with modem developments through membership and participation in professional organizations, regular review of key periodicals, and an awareness of the latest standards and criteria for professional practice. Key professional organizations for the traffic engineer include the Institute of Transportation Engineers (ITE), the Transportation Research Board (TRB), the Transportation Group of the American Society of Civil Engineers (ASCE), ITS America, and others. All of these provide literature and maintain journals, and have local, regional, and national meetings. TRB is a branch of the National Academy of Engineering and is a major source of research papers and reports. Like many engineering fields, the traffic engineering profession has many manuals and standard references, most of which will be referred to in the chapters of this text. Major references include Tra.c Engineering Handbook [I] Uniform Vehicle Code and Model Trafic Ordinance [2] Manual on Uniform Trafic Control Devices [3] Higlzway Capacity Manual [4] A Policy on Geometric Design of Highways and Streets (The AASHTO Green Book) [5]

REFERENCES 1s A few of these have had major updates and revisions since 2000, including References 1, 3, 4, and 5. Most standxds such as these are updated frequently, usually on a 5- or 10-year cycle, and the traffic engineer must be aware of how changes in standards, criteria, methodology, and other aspects will affect the practice of the profession. Other manuals abound and often relate to specific aspects of traffic engineering. These references document the current state of the art in traffic engineering, and those most frequently used should be part of the professional’s personal library. There are also a wide variety of internet sites that are of great value to the traffic engineer. Specific sites are not listed here, as they change rapidly. All of the professional organizations, as well as equipment manufacturers, maintain Web sites. The federal DOT, FHWA, NHTSA, and private highway-related organizations maintain Web sites. The entire Manual on Uniform Trufic Control Devices is available on-line through the FHWA Web site. Because traffic engineering is a rapidly changing field, the reader cannot assume that every standard and analysis process included in this text is current, particularly as the time since publication increases. While the authors will continue to produce periodic updates, the traffic engineer must keep abreast of latest developments as a ]professional responsibility. 1.7 Metric versus U.S. Units In the preface to the second edition of this text, it was indicated that the third edition would be in metric units. At the time, legislation was in place to require the conversion of all highway agencies to metric units over a short time period. Since then, the government has once again backed off this stance. Thus, at the current time, there are states continuing to use U.S. units, states continuing to use metric units (they had already converted), and an increasing number of states moving back to U.S. units after conversion to the metric system. Some of the key references, such as the Highway C,apacity Manual, have been produced in both metric and U.S. unit versions. Others, like the AASHTO Green Book, contain both metric and US. standards. Metric and US. standards are not the same. A standard 12,-ft lane converts to a standard 3.6-m lane, which is narrower than 12 feet. Standards for a 70-mi/h design speed convert to standards for a 120-km/h design speed, which are not numerically equivalent. This is because even units are used in both systems rather than the awkward fractional values that result from numerically equivalent conversions. That is why a metric set of wrenches for use on a foreign car is different from a standard US. wrench set. Because more states are on the U.S. system than on the metric system (with more moving back to U.S. units) and because the size of the text would be unwieldy if dual units were included, this text continues to be written using standard U.S. units. 1.8 Closing Comments The profession of traffic engineering is a broad and complex one. Nevertheless, it relies on key concepts and analyses and basic principles that do not change greatly over time. This text emphasizes both the basic principles and current (in 2003) standards and practices. The reader must keep abreast of changes that influence the latter. References 1. 2. 3. 4. 5. Pline, J., Editor, Trafic Engineering Handbook, 5th Edition, Institute of Transportation Engineers, Washington DC, 1999. Uniform Vehicle Code and Model Trafic Ordinance, National Committee on Uniform Traffic Laws and Ordinance, Washington DC, 1992. Manual on Uniform Trafic Control Devices, Millennium Edition, Federal Highway Administration, Washington DC, 2000. (Available on the FHWA Web site-www.fhwa.gov.) Highway Capacity Manual, 4th Edition, Transportation Research Board, Washington DC, 2000. A Policy on Geometric Design of Highways and Streets, 4th Edition, American Association of State Highway and Traffic Officials, Washington DC, 2001