This article illustrates the development and use of intelligent vehicles and automated highways to solve the increasing traffic problem. Small networks of computers installed in vehicles and along selected roadways could closely coordinate vehicles and harmonize traffic flow, maximizing highway capacity and passenger safety. A driver electing to use such an automated highway might first pass through a validation lane, similar to today's high-occupancy-vehicle (HOV) or carpooling lanes. The system would then determine if the car will function correctly in an automated mode, establish its destination, and deduct any tolls from the driver's credit account. The article also highlights that basic to the automated-highway schemes are computer simulations to indicate that such systems may be the least expensive way to increase highway throughput. The California Partners for Advanced Transit and Highways (PATH) Program at the University of California has developed the technology whereby magnets buried at intervals in the roadbed would be sensed by magnetometers in vehicles, providing a way to monitor their location and velocity.


Anyone who drives to work in one of America’s metropolitan areas knows that highway traffic congestion is getting worse. Average travel speeds on the crowded commuter corridors near large U.S. cities drop to about 36 miles per hour at rush hour, leading annually to some 5 billion collective hours of delay and estimated productivity losses of $50 billion nationwide. Meanwhile, the cars, trucks, and buses caught in chronic traffic jams waste vast amounts of fuel as they emit copious quantities of exhaust. Although the public may be loathe to face it, the unimpeded mobility of the automobile—considered a basic birthright by many Americans— is threatened by traffic-choked roadways.

The traditional solution has been to construct more and larger roadways, but that is no longer seen as a viable option by transportation planners, due to the high financial, social, and environmental costs of such giant projects. More efficient use of the existing road network using advanced technology seems to be the answer, but exactly what form that system should take is the subject of intense debate among the diverse groups that comprise the country’s transportation community—federal, state, and local government agencies; industry; academia; trade associations; and consumer and public-interest groups.

“Somehow we need to better meet the seemingly unsatisfiable demand for the freedom and mobility provided by cars and other vehicles,” said Gene MacCormick, senior vice president of Parsons Brinkerhoff Inc., a Washington, D.C.—based transportation consulting firm. “We have to find ways to operate the existing system more efficiently and effectively.”

One approach would be to develop automated highways that feature a lane or set of lanes on which vehicles equipped with specialized sensors and wireless communications systems could travel under computer control at closely spaced intervals, perhaps in small convoys or “platoons.” Vehicles could be temporarily linked together in communications networks, which could allow the continuous exchange of information about speed, acceleration, braking, obstacles, and so forth, said James Killings, program manager for intelligent transportation systems (ITS) at the General Motors Technical Center in Warren, Mich. Small networks of computers installed in vehicles and along selected roadways, he explained, could closely coordinate vehicles and harmonize traffic flow (for example, reducing speed fluctuations and traffic shock waves), maximizing highway capacity and passenger safety.

Platoons would resemble electrically coupled railroad trains, Rillings said, forming, splitting, and rejoining as required. Any system malfunctions could result in minor collision damage as the vehicles’ speeds would be similar.

Automatic Driving

A driver electing to use such an automated highway might first pass through a validation lane, similar to today’s high-occupancy-vehicle (HOV) or carpooling lanes. The system would then determine if the car will function correctly in an automated mode, establish its destination, and deduct any tolls from the driver’s credit account. Improperly operating vehicles would be diverted to manual lanes. The driver would then steer into a merging area, and the car would be guided through a gate onto an automated lane. An automatic control system would coordinate the movement of newly entering and existing traffic. Once traveling in automated mode, the driver could relax until the turnoff. The reverse process would take the vehicle off the highway. At this point, the system would need to check whether the driver could retake control, then take appropriate action if the driver were asleep, sick, or even dead.

The alternative to this kind of dedicated lane system is a mixed traffic system, in which automated and nonautomated vehicles would share the roadway. Rillings noted that this approach requires more-extensive modifications to the highway infrastructure, but would provide the biggest payoff in terms of capacity increase.

In fact, a spectrum of approaches can be envisioned for highway automation systems in which the degree of each vehicle’s autonomy varies, Rillings said. On one end of the range would be fully independent or “free-agent” vehicles with their own proximity sensors that would enable vehicles to stop safely even if the vehicle ahead were to apply the brakes suddenly. In the middle would be vehicles that could adapt to various levels of cooperation with other vehicles (platooning). At the other end would be systems that rely to a lesser or greater degree on the highway infrastructure for automated support. In general, however, most of the technology would be installed in the car, he said.


Sensing the Environment

A vehicle might use several approaches to sense its environment, said C. John MacGowan, chief of the Federal Highway Administration’s Intelligent Systems and Technology Division in Arlington, Va. To keep lanes, steer, and find location, magnetometers might be used to sense magnets buried in the roadbed. Alternatively, visual sensors might monitor highway marking tapes installed on the roadway, or intelligent video-imaging systems could track painted lane-boundary stripes. Obstacle detection and collision avoidance could be handled by millimeter-wavelength radar or infrared laser-ranging systems, or perhaps advanced video-imaging systems. “Eventually, I would expect that [sensor] data-fusion techniques would be used on advanced vehicles to minimize the amount of sensor technology each car would have to carry,” MacGowan said.

Toyota’s automated-highway-system vehicle features laser-ranging sensors, electronically controlled steering, throttle and braking systems, and a special navigation and warning dashboard display.

Accelerometers coupled to various actuators in a vehicle could manage steering, braking, and throttle systems to maintain its proper velocity and position. “The choice of wireless communication system would depend on the type of automation,” Rillings said. Of course, all this extra equipment would raise vehicle costs, which is one of the controversies surrounding automated highways.

MacGowan stressed that one key to developing suitable vehicles was the early adoption of an open-system architecture—the framework within which individual information, services, and functions (such as traffic monitoring and emergency support) can be developed. “We need an architecture that doesn’t scare the manufacturers away, because they’re going to have to work with it,” he said.

“We need to develop a compatible, interoperable system architecture, which is not there today,” said Ivy Renga, manager of the Intelligent Vehicle and Highway System Program for Chrysler Corp. in Madison Heights, Mich. “Take a look at electronic-toll-tag technology. Today, there are 20 companies with 20 versions of the technology, and none are compatible. Trucks must have mosaic of electronic tags to use these systems when they go cross-country. We need to set some goals and develop some national standards.”

Traffic Modeling

Basic to these automated-highway schemes are computer simulations to indicate that such systems may be the least expensive way to increase highway throughput, said Steven Shladover, deputy director for the California Partners for Advanced Transit and Highways (PATH) Program at the University of California, Berkeley, a research program that has been studying traffic issues since 1986. “We’ve done a great deal of detailed computer modeling. Our conclusion is that automation could double or even triple highway capacity.” For example, a typical highway lane can accommodate approximately 2,000 vehicles per hour. With automation, that capacity could be expanded to 6,000 per hour, depending on the spacing of entrances and exits.

The PATH Program has developed the technology whereby magnets buried at intervals in the roadbed would be sensed by magnetometers in vehicles, providing a way to monitor their location and velocity, Shladover noted. This approach could cost around $10,000 per mile to install, far less than the millions of dollars to build each mile of new highway, he said.

Shladover also cited the energy and environmental arguments that favor highway automation: “The fuel consumption and exhaust emissions of a motor vehicle is related directly to its specific driving cycle. If you can smooth out the traffic flow, vehicles can run at constant speed, which increases mileage and reduces air pollution.” Furthermore, “with platoon spacing set at a half a car length, cars can draft off each other, reducing drag by half.” This arrangement, Shladover added, could result in a 20-percent boost in fuel economy and similar-size cut in emissions.

Many members of the transportation community doubt these claims, however. “The computer models and studies that indicate that automation could double, or even triple traffic capacity are not accurate,” said Renga. “On paper, an automated highway system looks like a solution to future traffic problems, but technical feasibility has not been proven beyond a few lab and controlled test track demonstrations. These technologies have to be pretty much foolproof; otherwise, there’s no way to avoid the legal liabilities involved.”


Future highways may incorporate automated vehicle lanes accessible from validation/ transition lanes, which would check each vehicle’s computerized driving system.

The demonstrations are certainly useful, Renga said, but as yet there’s no consensus: “All the stakeholders need to sit down, find common ground; and then go on from there.”

Automated Demonstration

The most celebrated demonstration of traffic automation took place last August on a stretch of California freeway near San Diego. The experiment was conducted by the National Automated Highway System Consortium (NAHSC), a public/private partnership authorized by Congress in the Intermodal Surface Transportation Efficiency Act (ISTEA) of 1991 to perform long-term research on automated highway systems (AHS) for approximately seven-and-a-half years. In late 1994, the U.S. Department of Transportation (DOT) awarded the contract for this work to the NAHSC, which comprised Bechtel, Delco, Caltrans, Carnegie Mellon University, General Motors, Lockheed Martin, Parsons Brinkerhoff, PATH, and Raytheon. GM’s James Rillings served as the NAHSC program manager.

Eighty percent of the funding for the AHS program came from DOT, with the remainder being put up by its nongovernment partners. ISTEA stipulated that a demonstration of the program’s interim progress was to be conducted in 1997. “Congress decided it was time to get serious about addressing the congestion problem by getting automated highway technology off the drawing board and onto the road,” MacGowan said. The final product of the NAHSC program would be a fleet of enhanced vehicles for test and evaluation.

“It seemed important that the long-term research effort should be led by DOT, because leadership is needed to get the fragmented highway and transport community to focus on the real issues of traffic congestion and safety over an extended period,” Parsons Brinkerhoff’s MacCormick said. “AHS was really the first time we looked at the highway system as an integral system that includes the vehicle, the infrastructure it rides on, and the driver behind the wheel.” Approximately $50 million was spent on AHS development and demonstration. Tens of thousands of high-strength ceramic magnets were embedded in a 7.6-mile section of Interstate 15. Eight Buick LeSabres were modified with about $200,000 of automation equipment each, most of which was stowed in the trunk. This apparatus included a throttle actuator with a motor under the hood and controller in the trunk, a steering actuator developed by Delphi Saginaw that uses a motor attached to steering column and controller in trunk, a brake actuator developed by Delphi Chassis, a car-to-car radio communications link in the trunk, magnetometers in the front and rear bumpers, a motion sensor at the car’s center of mass, a dc/ac-inverter 110-volt power supply, and a ranging radar behind the grille supplied by Delco Electronics. Computer control was provided by a pair of 166-megahertz Intel Pentium processors. Data transfer between cars took place at 50 times per second.

The augmented cars “ran a total of about 8,000 miles, carried 4,000 passengers, and had no safety incidents,” Rillings said. Ongoing demonstrations of vehicle platooning highlighted the test. “The eight-vehicle platoon ran at 18-foot intervals at 65 miles per hour,” he said. “Surprisingly, almost everything we tried worked pretty well.” Another surprise was that “the vision-based technologies are reliable as other types of sensing technologies, like magnetic markers.”

Running in tight formation, “feels rather close, especially at first,” Rillings said, adding that “it’s really exciting for about the first 15 seconds, then it gets really dull. It’s like driving with a chauffeur.”

Rillings observed a phenomenon that is “interesting and a bit counterintuitive—older drivers seemed more willing to accept the automation. We guess they feel that way because they’ve seen more major technical progress and change. Younger drivers haven’t, and they’re less trusting of the new technology.”

The AHS technical-feasibility demonstration also witnessed other similar automated feats by trucks using video system to keep lanes and detect obstacles. This part of the demonstration was conducted by Eaton VORAD Technologies in Southfield, Mich. Toyota and Honda also showed their versions of intelligent vehicles, which were equipped similarly to the Buicks. The Toyota automobile, for example, featured a lane-departure warning system that alerts the driver when the vehicle leaves the lane unintentionally and corrects the vehicle path if the driver fails to respond. It also had an adaptive-cruise-control system that automatically sets the following distance to the preceding vehicle. At the heart of the Toyota system is an advanced image-processing system and several laser-ranging sensors.

Stakeholder Responses

Now that the AHS demonstration has been completed, DOT has asked ITS America, a Washington, D.C.—based group of more than 1,000 member organizations drawn from the transportation community, to serve as the focal point for stakeholder responses to the demo’s message. The idea is come to some consensus regarding the path of future development. After that, DOT plans to form several working groups to focus on the four major vehicle platforms that will take part, according to Richard Bishop, leader for intelligent-vehicle activities at ITS America: light vehicles (cars, small trucks, and vans), commercial vehicles (trucks), transit vehicles (buses), and special vehicles (ambulances and snowplows).

“The demo was the culmination of the AHS work,” Bishop said. “I believe it created a shift in the thinking of the public- and transportation-policy makers, bringing what was a nifty idea that’s far in the future to the realization that automated cars are nearer than we thought. That’s important because in the transportation business, technology is frequently not the barrier. More often it’s people’s attitudes and assumptions as to what is really possible.”


Both automated highway lanes and intelligent vehicles will require special sensors, controllers, and communications devices to coordinate traffic flow.

In the meantime, the NAHSC was allowed to lapse. Reportedly, a budget crunch at DOT and industry pressure for a shorter-term focus on safety led to a re-evaluation of the effort. Said MacGowan, “The thought regarding AHS was: ‘That’s fine for 2020, but what are you going to do about today?”’ Another transport expert, who wanted to stay anonymous, put it this way: “The more near-term technology is in closer alignment to the desires of private interests.”

The result of the change is the safety-oriented Intelligent Vehicle Initiative (IVI), which MacGowan noted is being built out of the groundwork laid down by the NAHSC, the National Highway Traffic and Safety Administration’s ongoing research on collision avoidance and driver/vehicle interfaces, and the NHTSA’s specialized work on trucks and buses. Whereas the AHS was a strong public/private partnership with the goal to build a prototype system, he said, the IVI is different: “The government is not sure exactly where we want to go. That’s why we’re polling the stakeholders via ITS America, to find the federal role.” The plan is to have prototype technologies in a couple of years, with field operations and testing following a few years later.

With the IVI, the new higher priority is improved safety, with mobility-enhancing systems a secondary goal. Certainly, safety enhancement is a laudable objective. Driver error is cited as the primary cause in about 90 percent of all police-reported vehicle crashes, and advanced safety technology could help. Preliminary estimates by the NHTSA show that rear-end, lane-change, and roadway-departure crash-avoidance systems have the potential to reduce motor-vehicle crashes by one-sixth or about 1.2 million crashes a year. Such systems may take the form of warning drivers, recommending control actions, and introducing temporary or partial automated control in hazardous situations.

“We want to find the most cost-effective approaches,” MacGowan said. The technology resulting from the IVI must be commercially viable and acceptable to drivers, with near-term implementation. It is also highly likely to be in-vehicle technology, rather than part of the highway infrastructure.

Adaptive cruise controls (ACCs) are probably the furthest along of these types of technology. ACCs are automatic speed regulators that also maintain a safe distance from the vehicle ahead. The device “senses a preceding car, monitors its distance and speed, and, if it decides there’s danger, emits a warning or may even cut the throttle or engage the brake,” said Chrysler’s Renga. Mitsubishi has already marketed an ACC system; Mercedes-Benz, BMW, Volkswagen, and Toyota plan to market the technology in their luxury cars.

According to Bob Ervin, head of the Engineering Research Division at the University of Michigan’s Transportation Research Institute in Ann Arbor, the development of ACC systems is a tricky issue. “First, the reliability of the technology has to be on the order of antilock-braking systems. It has to have a graceful or benign breakdown mode. In the case of ACC, the system falls into a coast mode.

“A tougher, more subtle issue,” Ervin added, “is what renders the system understandable to the driver—in other words, the details of the human/machine interface.” With ACC, the driver is placed in a new kind of supervisory role. “You’reentering a new area for automobiles—devices that characterize the environment and then respond in a way that the driver recognizes as appropriate. Of course, this is all colored by the driver’s expectations of how the system should operate.”

For example, say somebody is tailgating you, and the ACC responds to a false target and slows your car. The tailgater, who can see you have no rational reason to slow down, could become angry with you. “The machine has violated the following driver’s expectations,” Ervin said; this area of research “is what we call sociotraffic.” These kinds of difficulties will result in ACC systems being detuned, at least initially, “to keep them from making trouble, but that will make them less effective as well.”


The trunk of Toyota’s AHS vehicle contains early breadboard versions of computerized vehicle and steering controllers plus Global Positioning System-based navigation.

AHS Overseas

The trend toward developing automated highways seems to be strong in Japan and Europe. The Japanese government is working with Japanese automakers on the technology in the Advanced Cruise Assist Flighway System Research Association, which organized automated-highway demonstrations in 1995 and 1996. The European Community is also participating in this type of research focusing initially on enhancing the mobility of freight. The Dutch Ministry of Transport, Public Works, and Water Management is working with Daimler-Benz, BMW, Fiat, Renault, and Volkswagen in the Automated Highway System European Analysis.

The same Dutch ministry plus the Dutch Organization for Applied Scientific Research (TNO) and the European Union are sponsoring a demonstration of their Automated Vehicle Guidance (AVG) System in mid-June in Rijnwoude, the Netherlands. “AVG is one of the most important innovations in the transport system,” said G. R. M. Jansen, managing director of TNO traffic and transport. “It begins with small systems [the automatic maintenance of a safe distance or direction] and ends with a completely automated transport system.” The Dutch demonstration is “a good way to put AVG on the agenda of all the parties involved and provide a new push for international cooperation and coordination in this field,” said a ministry spokesman.

European Community involvement in this technology is progressing under the Telematics for Transport, Fourth Stage Research Program. One effort is CHAUFFEUR, a wireless radio link between two trucks (provided by Daimler Benz and IVECO), only the first of which will be operated by a driver. The trucks will drive very close to each other at highway speeds, using video imaging to keep lanes as well as video registration and infrared signals to maintain a safe distance. This technology is the first step toward truck platooning.

Another European Community—supported development project is its anticollision, autonomous-support, and safety-intervention system, which is an adaptive-cruise-control program involving Jaguar, Volvo, Renault, and Rover.

In addition, Urban Drive Control is an effort to enhance traffic flow in cities and reduce pollution. With this technology, road beacons are used to calculate the favorable speed to improve traffic mobility which is then recommended to drivers or imposed automatically. This technology, which is being tested in Turin, Italy, is being supported by Fiat, PSA, Jaguar, and Renault. Clearly, incremental steps will be needed to make any progress toward fully automated highways. ITS America’s Bishop offered several possibilities for early introduction. One early candidate for instituting highway automation technology might be public or private bus systems or a state’s highway-maintenance vehicles. “These are closed systems,” he said. “What better setup could there be for early introduction?” An alternative would be “the huge private freight terminals at ports, where trucks move products to and from large storage areas.”

He also offered a concept for introducing automation to public highways. “The idea is to convert incentive (high-mobility) lanes such as HOV (carpooling) lanes or the ‘new alternative fueled vehicle lanes’ to semiautomated vehicle lanes.”

Indeed, state transportation departments have expressed some interest in this kind of approach. Tom Schmitt, state engineer for the Arizona DOT, said that his agency is studying the possibility of setting up an “intelligent express lane, perhaps using magnetic guidance” on the 100-mile stretch of Interstate 10 between Tucson and Phoenix, which has become a busy traffic thoroughfare. “Right now, I—10 is two lanes each way,” he said, “and we want to avoid having to widen it. Of course, we’re realists and there’s no funding or suitable cars yet, but the AHS demo showed that the technology may not be that far off in the future.”