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1、外文文献资料ADVANCED VEHICLE/HIGHWAY SYSTEMS AND URBAN TRAFFIC PROBLEMS OTA PROJECT STAFF SUMMARYTraffic congestion plagues every major urban area in the country, costing millions of dollars annually in lost time from delays and contributing to serious air quality problems. While many approaches to these
2、issues have been tried - including building more roads, creating high occupancy vehicle (HOV) lanes, and promoting car pooling and public transportation -none has achieved more than modest success. Advanced Vehicle/Highway Systems (AVHS), an umbrella term for several interdependent vehicle and road
3、technologies, offer potential for reducing congestion and the air pollution it engenders, and for improving highway safety.The term AVHS includes technologies for:automatic vehicle identification and billing;weighing vehicles in motion;collision warning and avoidance;driver information and route gui
4、danceadvanced traffic operations control and optimization; andautomatic vehicle control - both steering and headway.OTA concludes that AVHS technologies now available can increase roadway efficiency and throughput by 10 to 20 percent, make travel time more predictable, improve safety, and cut down h
5、armful emissions, although by themselves they cannot solve our urban traffic problems. If road capacity is increased and road travel made more desirable, more motorists can be expected to take to the roads, counteracting some reductions in congestion. If even moderate success is to be achieved in co
6、mbating these issues in the near term, other strategies, such as car pooling, HOV lanes, use of alternative fuels, congestion pricing, and other forms of transportation systems management must also be pursued aggressively.However, emerging AVHS pose no conflicts with other traffic management strateg
7、ies, can be used in conjunction with them, and indeed, may facilitate certain aspects. These multiple benefits from AVHS argue for the immediate further development of AVHS and greater investment in research, development, and operational testing. More aggressive Federal leadership in organizing and
8、supporting research could assist States and localities in addressing urban transportation infrastructure problems. States (notably California) and some universities have established cooperative public/private programs that provide good models. OTA finds that substantial short-term national advantage
9、s could come from Federal policies and programs to encourage implementation of advanced traffic operations control systems. Through large-scale, high-profile, government supported research programs abroad, such as Prometheus and Drive in Europe and various others in Japan and other countries, foreig
10、n transportation research has advanced far beyond that in the United States in many areas. As AVHS technologies are implemented, extensive in-vehicle and roadside instrumentation will be needed. The size of this potential market and the strong priority given AVHS abroad raise concern that the United
11、 States will lose out in developing and producing “transportation electronics” products unless steps are taken soon.Most in-vehicle systems are dependent for successful operation on beacons, detectors, and other components based in the infrastructure and usually supplied by the public sector. Withou
12、t assurance that local or State governments will equip the transportation network with such beacons and detectors, manufacturers of in-vehicle systems are reluctant to press ahead, despite the threat of foreign competition. Existing limitations on the use of Federal grant money for these systems cou
13、ld be eliminated, and other types of urban transportation assistance could be made contingent on the installation of these systems. Federal policies could encourage and facilitate the necessary interjurisdictional coordination between agencies that manage freeway and arterial traffic.Federal partici
14、pation in testing and demonstration programs of vehicle identification, driver information, and collision warning and avoidance technologies could speed advancement of in-vehicle equipment. Government leadership in addressing standardization issues early would also aid development of these technolog
15、ies. Finally, how drivers interact with AVHS technologies is not fully understood. Attention to safety and human factors is a top priority, and active participation in these areas by Federal agencies responsible for highway safety is warranted.OTA concludes that Federal effort and dollars invested i
16、n assisting State and local governments in moving ahead with AVHS could do double duty. They could support much needed programs to address urban traffic congestion as well as boost industry by helping create the public infrastructure necessary to communicate with advanced products that are almost ma
17、rket ready.In February 1989, the Subcommittee on Transportation of the Senate Committee on Appropriations requested that OTA examine advanced vehicle and highway technologies and assess their potential to increase the capacity of the transportation infrastructure. This document examines a wide range
18、 of these technologies, but focuses on those commonly known as advanced vehicle/highway systems (AVHS) and on related technologies that affect or complement AVHS.The term AVHS refers to advanced technologies that are applied to motor vehicle transportation and traffic operations, such as technologie
19、s for:automatic vehicle identification and billing;weighing vehicle in motion;collision warning and avoidance;driver information and route guidance;advanced traffic signal control and optimization;automatic incident detection; andautomatic vehicle spacing both steering (lateral) and headway (longitu
20、dinal).AVHS does not include technologies used in vehicle manufacture, road construction, or mass transit system design and operations.Domestic research in most areas of AVHS was active in the 1960s, but tapered off during the 1970s as funding and interest declined. Recently, AVHS has received renew
21、al attention in the United States for several reasons. As air pollution and traffic congestion have worsened, many see AVHS as tools for increasing road safety, reducing traffic delay and incident response time, and increasing traffic capacity. Since a large portion of congestion is caused by accide
22、nts, significant benefits can result from reducing both the number of accidents and the time it takes to clear the roadway after an accident occurs - actions that do not require AVHS, but can be made easier by them. Others see AVHS as a means for reducing fuel consumption and air pollution, making c
23、ommercial shipping more efficient, and easing the driving task for physically limited drivers. But perhaps the major reason for the renewed interest is the high level of attention being given AVHS by European and Japanese researchers. Europe and Japan both have high-profile government-sponsored rese
24、arch and development programs under way which include participation by industry and academia. As U.S. participation in these foreign programs is limited - and, in some cases, prohibited automobile manufacturers and technology experts familiar with AVHS raise concerns that the United States is fallin
25、g behind in research and technology development. U.S. manufacturers fear that they will beat a competitive disadvantage relative to foreign firms when AVHS “products” enter the motor vehicle market.Advanced Driver Information (ADI) SystemsADI systems give drivers current information on road and traf
26、fic conditions so that they can plan their routes to avoid areas of congestion. ADI systems range from one-way audio communications to interactive video communications, and some of the more advanced systems plan routes automatically after the driver has provided origin and destination information. T
27、he systems can be home-, office-, or vehicle-based. While they can operate independently, they are much more useful with information about the transportation infrastructure - current roadway and traffic conditions.Traffic reports on commercial radio stations represent the most basic of the ADI techn
28、ologies. in limited use, highway advisory radio and its variations use dedicated frequencies (usually at the ends of the broadcast spectrum) to transmit traffic information. Tested, but never implemented, automatic highway advisory radio (AHAR) can automatically do some or ail of the following:signa
29、l the driver that an advisory notice is about to be broadcast;mute the program the driver is currently listening to; andtune the radio to the AHAR frequency.Teletext and videotex systems, which have been used in Europe for route planning, are usually accessed from the home or office and provide trav
30、elers with written information on traffic conditions. interactive versions of such systems allow drivers to query databases for optimal path information and to receive written route instructions. Vehicle-based navigation systems automatically track vehicle location, and some, using computerized map
31、bases, show the current location on an electronic map display of the surrounding area. When the driver enters origin and destination information, these systems can provide detailed advice on which streets to follow and when to turn. Enhanced versions of such devices that have communication links to
32、the infrastructure are being developed; these allow the incorporation of current road and traffic information into route guidance. Despite the diverse technologies involved in driver information systems, the systems all aim at warning motorists of congestion, so they can alter their routes or resche
33、dule their trips to reduce tie ups. Similarly, navigation devices - even those without communication links - have potential to reduce traffic congestion by informing motorists of routes that can minimize time spent and distance traveled.Advanced Traffic Management SystemsATMS include urban traffic c
34、ontrol systems, incident detection systems, highway and corridor control systems, and ramp metering systems. Urban traffic control systems coordinate traffic signal operations throughout a given area based on traffic patterns as measured by detectors in the roadway. in the United States, highway con
35、trol systems almost always remain separate from urban traffic control systems, and there are few integrated systems in place thus far. ATMS hardware consists of sensors, traffic signals, ramp meters, changeable message signs, and communication and control devices integrated into a single system. Thi
36、s allows for surveillance and control of traffic in areas so equipped. Because current traffic detectors, which are usually embedded in the roadway, are susceptible to frequent failure, new methods of measuring traffic are being investigated to improve the performance and reliability of the systems.
37、 These include among other technologies, infrared sensors and machine vision systems (video cameras linked to a computer that analyses the images to generate traffic flow and congestion information).One of the more advanced urban traffic control systems in place in this country is the Automated Traf
38、fic Surveillance and Control system (ATSAC), a computerized traffic signal control system installed by the Los Angeles Department of Transportation. Based on the Urban Traffic Control System Enhanced software package developed by the Federal Highway Administration (FHWA), ATSAC was put into operatio
39、n several weeks prior to the 1984 Olympic Games. Initial installation included 118 intersections and 396 detectors in a 4 square mile area centered at the University of Southern California and the Los Angeles Coliseum. It has since expanded to include areas of the San Fernando Valley and central bus
40、iness district for a total of 371 intersections. The airport and Westwood areas are targeted for later implementation, and by 1991, the system is expected to include 1,600 intersections. ATSAC is funded by a combination of FHWA, a traffic mitigation fund financed by developer fees, and distributions
41、 from the Petroleum Violation Escrow Account fund.ATSAC operators use color graphics workstations, which allow any portion of the surveillance area to be monitored at any desired level of resolution: from traffic flow data at the intersection Ievel (such as volume and occupancy) to a broader view of
42、 traffic behavior over a region. ATSAC gives the current status of any traffic signal in the network, allows manual override from the control center, and gives traffic flow data for any functioning pavement imp detector in the network. When first installed, ATSAC selected, usually by time of day, a
43、signal timing plan out of a library containing several plans. It has since evolved into a system that automatically selects (and switches) timing plans by matching current traffic patterns against historical data. Fine tuning of signal operations can be accomplished by manual override or automated c
44、ontrol of critical intersections. Critical intersection control allows the system to alleviate local congestion while still adhering to the overall strategy of the existing timing plan.To assist in traffic surveillance and incident management, closed-circuit television cameras are being installed at
45、 important intersections. These cameras, which are controllable from the traffic control center, can pan and zoom to provide a wide area of coverage or a detailed view over a smaller area. They assist in incident management and provide visual confirmation of traffic behavior to the Operators. A 1987
46、 study to determine the traffic flow and economic benefits of using ATSAC concluded that significant improvements were attained in all areas measured: travel time (13 percent decrease), number of stops (35 percent decrease), average speed (15 percent increase), fuel consumption (12 percent decrease)
47、, and vehicle emissions (-10 percent). computerized signal control also provided rapid detection of faulty sensors and the identification of unusual traffic patterns due to incidents. Estimated cost savings to motorists (business and truck trips only) as a result of lower operating costs and time sa
48、ved recovered the $5.6 million construction cost of ATSAC after only 8.6 months of operation. The annual operating costs are recovered with the first week of operation every year.One shortcoming of ATSAC for the greater Los Angeles area is that it relieves street congestion only. Freeway congestion
49、is not monitored or controlled by ATSAC, since freeway traffic falls under the authority of the California Department of Transportation (Caltrans). Although some traffic coordination does take place between Caltrans and the City of Los Angeles, the lack of an integrated traffic management system has been a severe limitation to the system. Recognizing this, the major transportation agencies in the Los Angeles area initiated the Smart Corridor demonstration. which will include selected city-operated surface