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ATMS technology - what we know and what we don't know.


As the backbone for the social and economic development of any country, a sound transportation system can promote business and facilitate communication by ensuring the proper movement of people and goods. Over the last few years, however, demand for the use of transportation facilities in the U.S. has increased at a rate much higher than that which can be absorbed by current systems. This phenomena, coupled with the lack of funding to construct new facilities and accommodate this additional demand, has been a major contributor to traffic congestion.

Recognizing the institutional impossibility of constructing new facilities that would satisfy current and future travel demand while preserving the environment, the Federal Highway Administration (FHWA) is pursuing the concept of Intelligent Vehicle--Highway Systems (IVHS).

IVHS is an ambitious multiyear, multibillion dollar research and demonstration program that aims at improving vehicle-highway system operation and management techniques for the post-interstate construction era. The main goal of the IVHS program, which will carry the FHWA into the 21st century, is to develop and implement state-of-the-art vehicle-highway management techniques and control systems that will effectively reduce congestion by optimizing the use of existing infrastructures. If successful, we will provide an increased level of safety, mobility, driver convenience, and environmental quality for both rural and urban areas.

This article explores the basis for this vision, thereby inviting transportation professionals to involve themselves in defining our traffic management systems of the future.

IVHS Components

The transportation technologies that will develop under the IVHS program are divided into five interrelated components: Advanced Vehicle Control Systems (AVCS), Advanced Traveler Information Systems (ATIS), Commercial Vehicle Operations (CVO), Advanced Public Transportation Systems. (APTS), and Advanced Traffic Management Systems (ATMS).

The ultimate goal of Advanced Vehicle Control Systems is to develop and apply technologies in ways that substantially improve throughput, level of service, and safety. For example, AVCS is developing technology in which the driver no longer drives; he or she becomes a passenger. Without human intervention, cars could journey from one place to another on designated highways that are suitably instrumented. More specifically, the use of radar for steering within a lane and for sensing neighboring vehicles are examples of such technologies. Another example is a braking system that regulates vehicle speed and minimizes the time separation (headway) of platooned vehicles.

Advanced Traveler Information Systems is the framework through which information is made available, not only to the driver, but to the general traveler. ATIS is composed of several elements. The first of which is the development of invehicle route guidance systems. This includes audio-visual aids such as electronic maps and highway advisory radios that enable the driver to select the best route. A second element is the development of models that optimize network routing and usage. The third element is the dissemination of information to travelers that allows for pre-trip and/or en route planning. An example of such information would be the message that congested highways have affected bus schedules or that high-occupancy vehicle (HOV) restrictions have been lifted. Another element of ATIS is quantification of driver behavior. This would entail developing models that replicate how people select routes, how they react to highway incidents, and how they select their mode of travel.

Commercial Vehicle Operations addresses the special needs of commercial traffic. It encompasses many of the ATIS aspects and enables dynamic fleet management. CVO also encompasses invehicle diagnostic systems, automated vehicle identification and certification, and driver performance systems. These systems will alert professional drivers of possible vehicle malfunctions, log arrivals at checkpoints and/or jurisdictional boundaries, and measure driver performance (such as alerting a driver who is experiencing fatigue).

Advanced Public Transportation Systems addresses the needs of nondrivers: people who indirectly use the highway system. This component of IVHS is concerned with the optimal utilization of mass transportation systems such as buses, light rail, subways, and any form of high occupancy vehicles such as carpools and vanpools. APTS can make a significant difference in providing mobility as information on mass transit facilities will be made available to drivers. For example, once the origin and destination of a trip is determined, a driver could be made aware that re-routing his or her trip to use other transportation modes could make the travel time shorter and/or safer.

Most important of all aspects of the IVHS program is Advanced Traffic Management Systems, the very backbone of IVHS. ATMS consists primarily of three aspects. One aspect is the development of surveillance systems to monitor the operational status of a roadway network. A second aspect is the development of real-time, traffic-adaptive control systems which, through the feedback provided by the surveillance system, adapt network control such as traffic signals, freeway ramp meters, messages on electronic signs, etc., for optimal performance. A third aspect is the development of system operator support systems (expert systems, simulation models, etc.) to enable and facilitate real-time control and management of the network.

What We Can Do Today

In the 1990's, congestion reduction must be approached by spreading demand over existing facilities, optimizing their use, and providing control in an adaptive fashion. To do this, we need areawide ATMS operations centers deployed in all large metropolitan areas. Increasing the number of ATMS will help produce maximum traffic-moving capability of existing streets and highways throughout the country. The implementation of ATMS requires: 1. Deployment of areawide control system infrastructure,

including necessary institutional arrangements

and agreements, where such infrastructure

is currently lacking. This will facilitate

the collection of traffic data and other information

required for real-time areawide control. 2. Research and development activities on advanced

traffic management measures, such

as wide-area detection, control, and assignment

algorithms based upon real-time data.

The products resulting from these activities

must work to advance the state of the art and

continue to push, in an accelerated manner,

the state of the practice. 3. Use of selected areas as real-world test beds

to evaluate and demonstrate research results.

This will increase the acceptability and implementation

of research results.

While implementation of ATMS technology can do much to improve the flow of traffic on congested freeway and arterial streets, it can also provide the infrastructure and create the market for the more advanced invehicle guidance systems, automated vehicle identification and location systems (AVI/AVL), and automated control systems.

Some of the system requirements for ATMS include: * Surveillance and detection systems. Surveillance

and detection are crucial in a traffic control

system. The surveillance and detection

system could be a police officer at the corner

or a smart set of detectors on the highway. In

either case, a mechanism to transmit that information

back to a control center is required. * Real-time, traffic-adaptive control. ATMS

must be responsive to traffic flow and work in

real time. The implemented traffic management

strategy should link real-time traffic

monitoring, short-term travel forecasting, and

electronic route guidance to integrate network-wide

control and allow for a comprehensive

traffic management system. Data that is

transferred to the control center must be current

so that an effective strategy can be devised

and implemented quickly. * Effective incident control and management.

Incident management is crucial. However, before

an incident can be managed, it must be

detected and verified, and an appropriate response

plan must be made. The response

plan must integrate onsite tactics (vehicle

clearance and required maintenance), diversion

strategies (streets involved, changeable

message signs, radio broadcasts, and traffic

signal timing during diversion), and cover

both surface streets and freeways. * Route guidance information. ATMS must collect

and disseminate routine guidance to vehicles

based on actual traffic conditions.

These systems will also be able to predict the

number and type of vehicles that will be on a

particular road segment and could conceivably

give special instructions to different

classes of vehicles. * Integration of components. ATMS must integrate

ATIS, CVO, APTS, and eventually AVCS.

Also, ATMS must provide the technology for

integrating freeways and surface streets such

that travel demand can be managed at a network-wide,

multimodal level.

In summary, the ATMS surveillance system identifies the presence of vehicles, locates disturbances in traffic flows, and identifies congestion points and accidents. Based on the traffic information collected, ATMS then permits real-time adjustment of traffic control systems. With intelligent traffic prediction algorithms, ATMS can also prevent traffic congestion by developing online traffic control measures based on anticipated degradation in the throughput of networks using current traffic volumes and origin-destination (OD) information. Ultimately, when in full integration with ATIS, CVO, and APTS, Advanced Traffic Management Systems can influence driver route choices and/or travel mode by indicating alternate routes to be followed (in case of incidents) or by simply redistributing part of the traffic to less congested routes during rush hours.

There are two major challenges in the development of ATMS: integration and forecasting. Integration will require the development of highly sophisticated systems and interfaces that must overcome hardware compatibility problems. That is, these systems must be flexible enough to interact with different equipment. Also, rather than analyzing and reacting to information, these systems must forecast and implement prior to degradation.

Immediate integration of these systems is vitally important. Congestion continues to grow, and it will become much more difficult to ensure our future mobility. Ironically, most of the technology needed to implement IVHS is already available. That is, many of the subsystems needed have been developed and, to a certain extent, have been implemented in isolation.

Preliminary ATMS applications in selected corridors have proven to reduce delay and travel time, improve the productivity of commercial fleets, enhance highway safety, produce energy savings, and improve or quality. However, the full development and implementation of ATMS requires the availability of comprehensive communication systems, surveillance systems, and proficient traffic analysis tools (such as traffic models).

The following three items need particular attention: communications, surveillance, and analysis.


We currently have most of the technology needed to satisfy the communications needs of ATMS. For instance, basic communication between detectors, controllers, masters, and a central computer is now available over different mediums. One must consider, however, that advanced control will likely require a substantial increase in the frequency and amount of data flowing among these components.

Of greater consequence is the need to establish communications between the traveler and the control center. This is the most effective way of influencing demand and, therefore, mitigating congestion. Providing accurate information on the operational status of the network to potential users will undoubtedly influence route selection, departure time, and possibly destination and mode. For example, a traveler might change his route if information on major obstructions affecting the planned route is available. He may even change his mode if an alternative is available and convenient.

One major pitfall is our lack of traveler behavior knowledge. How do people make choices relative to route, mode, and departure time (assuming they have that flexibility)? Before we engage in a proactive traffic control strategy, we must better understand what information will make travelers change their preset trip. How can we influence their decision-making processes? How amenable are they to change? Even if the information is always perfect and available, how many will take the advice? And, how many will make good decisions? All of these are crucial issues that need to be addressed and quantified to some extent. The success of proactive control depends on it.


The critical element of any advanced traffic management and control system is reliable data. Surveillance systems now in place usually report volume and occupancy information on a preset basis at selected locations within a network. However, the number of stations and the amount of information yielded by these systems may not be enough to ensure optimal control.

Traditional surveillance systems will not suffice within an ATMS environment. ATMS will need information on usage by lane, oversaturated locations and/or locations with excess capacity, the location and occurrence of recurring and nonrecurring congestion, location of weather influencing traffic (snow, fog, rain, etc.), a much improved method of incident detection, and, possibly, hazardous materials tracking and vehicle classification.

Even though these needs must be satisfied, it is not likely that all of this information will come from a surveillance system that relies solely on detectors. Economically, it is impossible to fully instrument a roadway network to the extent needed by IVHS. Instead, novel approaches must be developed to "fuse' data from police reports, "probe" vehicles (those which have two-way communication with the control centers), commercial fleets, emergency vehicles, etc., with the "detector" data, and generate the information necessary to provide dynamic, traffic-adaptive control.


Traffic analysis tools, for the most part, take the form of computer models. Because of the complexity of the congestion problem, it is no longer efficient to develop technical manuals or handbooks that outline a routine procedure to be followed for specific situations. It is adequate to develop a manual that addresses the issues of evaluating and optimizing the control or geometry of an intersection. It is not adequate to require practitioners to use the same manual to optimize all of the intersections within the same jurisdiction using this approach, as it does not take into account the impact of improvements made to the preceding or subsequent intersections. The major advantages of using traffic models are that they provide an environment where traffic control strategies can be tested and fine-tuned without having to disturb traffic, they avoid the risk of liability when problems in a strategy are detected only after implementation, and they save the capital required to acquire and install traffic control hardware so that strategies, which may or may not work, can be field tested.

It is imperative that traffic engineers "think" network-wide. Addressing a local problem will only result in the relocation of the same problem elsewhere. The scope of traffic control has grown to a more technically sophisticated science that requires the use of traffic models. This complexity stems from the fact that transportation planning, traffic operations, safety, mass transit, and other related surface transportation functions need to be integrated into a network-wide, transportation management system. Traffic models can do this and much more.

Traffic management, by definition, implies that more needs to be done with what we have. That is, it implies that we must maximize the use of current surface transportation facilities. The term "management" calls to mind the ability to study a situation, identify the possible options and, most importantly, activate a decision-making process that efficiently addresses the situation under study. A key factor in this process is the ability to develop quality alternatives. In many cases, the only viable way to evaluate and fine-tune control strategies is by using traffic models.

Proactive traffic management requires that practitioners define, explore, speculate, accommodate, and undertake engagement strategies that, for the most part, will not follow tradition. We cannot continue to time signals using 1930's methods and expect them to work. Present traffic conditions, such as driver behavior characteristics and type, number, and performance characteristics of vehicles, make these methods obsolete. Again, traffic models are the tools that will allow practitioners to test innovative control strategies suitable to address our current problems.

What We Need To Proceed

A lot has been accomplished; yet, a lot remains to be done. Some of the very basic modeling needs based on the current concept of IVHS include: * Dynamic traffic assignment models. * Real-time, traffic-adaptive signal control. * Optimal route diversion models. * System operators' support systems. * Freeway-surface street integrated control. * Generic simulation engines capable of testing

any new control logic. * Driver/traveler behavior models.

A key determinant of the success of Intelligent Vehicle--Highway Systems will be how users adjust their travel behavior in response to strategies designed to alleviate congestion conditions. Unfortunately, individual route choice modeling requires that explicit consideration be given to the tangled behavioral issues in driver/traveler decisions.

Due to the complexity of this factor, research in the area has concentrated on small, often isolated, components of the problem. For example, in an effort to gain further understanding, studies always confine the scope to approximately one origin and destination (OD) pair. Truly significant advances in the study and modeling of driver/ traveler behavior will have to evolve largely from data sources that currently do not exist. Another crucial activity is the development of simulation environments where the potential benefits from these technologies can be assessed. These are benefits to users, developers, State and local agencies, and other interested parties. For example, software that continuously regulates the speed and position of all vehicles can be used to simulate the effectiveness of Advanced Vehicle Control Systems. Occupancy of lanes, spacing between vehicles, merging, and exiting would proceed in accordance with protocol. When a vehicle leaves the roadway, the driver would recover conventional control. In fact, because a central computer may know each vehicle's immediate position and eventual destination, all vehicles on the automated highway could be directed in order to achieve some overall optimum such as maximum vehicle throughput. Disruptions in flow due to merging and lane changes could be minimized, and headway and lateral spacing between adjacent vehicles could be reduced to those levels needed for safe operation. From this simulation, one could assess the operational benefits of the system, the overall feasibility of the concept, and the technical merit by demonstrating strengths and deficiencies.

The worldwide, traffic engineering community has already outlined the systems of the future. These systems, which include ATMS, ATIS, CVO, APTS, and AVCS, hinge on the postulation that real-time, accurate traffic information will be the main weapon used to combat congestion. Given that these systems will enable the exchange of information between control centers and motorists, traffic professionals expect to maximize the use of networks by "spreading the demand" throughout the available facilities. But, how do we do this?

Let's briefly assume that these systems are installed. How would control center operators know how and when to divert traffic? How can they evaluate the effectiveness of a systemwide timing plan? How could they detect incidents and manage the network under emergency conditions? The first reaction is to answer by stating that these systems will have the smarts to perform such tasks. Where, or how, are these smarts going to be integrated into these systems?

The answer is very simple: these smarts are the output of traffic models. In essence, these systems must incorporate traffic models within them (transparent to the user) such that intelligent feedback can be given to the operators regarding what to do, when to do it, and how to do it, based on the specifics of the situation. The real benefit is that these tools are capable of considering the problems on a network-wide basis; therefore, implementation of the modeled recommendations will not simply relocate the problem from one location to another. Rather, the recommendations will be the best possible for the overall network. The bottom line is: These systems will not operate without traffic modeling support.

Summary and Conclusions

This article discussed some of the problems we are experiencing that have deterred our ability, as a profession, to provide adequate mobility. These include existing flaws in the state of the practice, our inability to bridge the gap between the state of the art and the state of the practice, and our professional inertia to change the way we do business.

We know what our problems are. We know that we cannot solve them with current technology or by accretion of new facilities. We are being challenged to develop a collective approach that maximizes the utility of our existing facilities by providing adequate management.

IVHS is an approach to managing and resolving these problems. In essence, it encompasses the fundamental restructuring of the U.S. transportation system in order to provide a viable, comprehensive solution to our surface transportation problems. As a profession, however, we are failing to develop a comprehensive strategic plan to implement IVHS. Most of the direction is coming from people other than those who actually operate our current systems. That is, the leadership being provided is not being influenced by practitioners--the same people we are expecting to use these systems once they are developed and deployed. We must engage in a grassroots campaign to incorporate practitioners' input into the plan. In effect, we are changing the way traffic engineering is, and will be, practiced in the United States.

In terms of technology, much of IVHS-ATMS could be implemented now. However, the present approach to an IVHS-type solution contains two basic flaws that would limit its effectiveness to mere improvement, rather than the full system redesign that may be needed: 1. We are attempting to apply advanced technologies

with a mindset that promotes the

use of procedures based on conditions and

assumptions that predate and indeed have

helped to create the existing problems. 2. We are focusing on advancing the state of the

art and not paying enough attention to pushing

the state of the practice. We must develop systems

and solutions that can be implemented.

We must pay attention to these deficiencies and

overcome them effectively. If we do, there is no

question that IVHS will be a viable solution.

The tactical plan currently being used to execute the IVHS program is also helping to achieve the success of IVHS. This plan comprises two basic elements: research and development, and field operational tests. This tactic, although very appropriate, must be aggressively pursued and sustained until the practicing community adopts and effectively uses IVHS technologies. We must (and will) succeed in developing and demonstrating these technologies in real-world implementations to prove their technical adeptness, establish credibility, promote their use, and, most importantly, create ownership. However, without the practitioner, this will not happen.

Remember when the slide rule was the principal tool for mathematical and trigonometric calculations? All of a sudden, someone developed a handheld, battery-operated trinket called a calculator. How much has this development changed the accuracy of calculations and the way people work?

How would you feel if, at that time, you had been asked to participate in the development of the calculator? If by now you have made the connection, you are right on track; if not, we are asking you to participate in the formulation of IVHS.

Notwithstanding, the dilemma is: How are we going to pull it off?

Alberto J. Santiago is the acting branch chief of the Traffic Systems Branch in the Intelligent Vehicle-Highway Systems Research Division of the Federal Highway Administration's Office of Safety and Traffic Operations, R&D. He was selected to participate in the Department of Transportation Fellows Program, and he received the FHWA Administrator Superior Achievement Award in recognition of his outstanding technical contributions in the area of traffic analysis and modeling.

Traffic Models

* Test and Fine-Tune Traffic Control Strategies

* no disruption of traffic

* no risk of liability

* reduced costs * The Only Way to Evaluate Many ATMS Control Strategies
COPYRIGHT 1992 Superintendent of Documents
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Copyright 1992 Gale, Cengage Learning. All rights reserved.

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Title Annotation:Advanced Traffic Management Systems
Author:Santiago, Alberto J.
Publication:Public Roads
Date:Dec 1, 1992
Previous Article:The impacts of alternative urban development patterns on highway system performance.
Next Article:The application of ground-penetrating radar in highway engineering.

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