Automated Highway Systems Research Articles

Improving Highway Design to Enhance the Performance of Automated Highway Systems

From the perspective of sprung vehicle dynamics, current highway design criteria are somewhat inadequate for fulfilling broad requirements of automated highway systems and automatic control vehicles. Therefore, in this study, we present a split layout of pavement friction, designed to counterbalance an insufficient superelevation and overcome unpredictable rolling instability. The proposed layout provides different friction pavements between a lane's left and right sides in a curve stretcher along a highway. Such a layout causes vehicles to be more stable in dynamic. In addition, no deficiency arises in setting superelevations, of which, the inclined cross-sections potentially cause side slipping under poor weather conditions. The optimal friction difference values are also illustrated in terms of the radius with respect to AASHTO's criteria. Finally, some implementation issues are also addressed.

Analyses of Vision-based Lateral Control for Automated Highway System

SUMMARY The stability and performance of a vision-based vehicle lateral control system are analyzed. Effects of look-ahead distance, vision delay, and vehicle speed on the performance of vision feedback control system are examined by using frequency domain and time domain methods. A measurement model of the vision system is derived from the point of view of multiple sensors. The quantization error of the vision system is analyzed and the way of extracting essential information for control is studied. Based on this analysis, some guidelines for the design of vision-based controllers are proposed. A design example is further illustrated for a vision system with a substantial time delay.

Automated highway systems

Currently, intelligent transportation systems are being developed and implemented in various forms. Advanced traffic management systems (ATMS), automatic traveler information systems (ATIS) and driver support systems are all a reality today. However, many challenges remain on the road to realizing a fully automated highway system (AHS). The complexity of developing large distributed systems such as AHS has raised warning flags in the computer science community. Unexpected complex interactions between the software and hardware can induce errors that can be fatal. The authors argue that these issues should provide a cautionary note to practicing engineers before deploying a fully automated highway system.

Large Scale System Issues in Automated Highway and Air Traffic Management Systems

Large scale systems typically consist of compositions of many interacting sub-systems performing various planning and control functions. Control for such systems is often arranged in a hierarchical structure, with high level scheduling functions concerned with optimality and efficiency issues and low level control functions implementing the desired high level objectives and dealing with system uncertainty and safety. This paradigm leads to interactions between the fields of optimization and control theory. In this paper, these issues are highlighted using two large scale applications: Automated Highway Systems (AHS) and Air Traffic Management (ATM) Systems.

Verified hybrid controllers for automated vehicles

The objective of an automated highway system (AHS) is to increase the safety and throughput of the existing highway infrastructure by introducing traffic automation. AHS is an example of a large scale, multiagent complex dynamical system and is ideally suited for a hierarchical hybrid controller. We discuss the design of safe and efficient hybrid controllers for regulation of vehicles on an AHS. We use game theoretic techniques to deal with the multiagent and multiobjective nature of the problem. The result is a hybrid controller that by design guarantees safety, without the need for further verification. The calculations also provide an upper bound on the performance that can be expected in terms of throughput at various levels of centralization.

Color machine vision for autonomous vehicles

Color can be a useful feature in autonomous vehicle systems that are based on machine vision, for tasks such as obstacle detection, lane/road following, and recognition of miscellaneous scene objects. Unfortunately, few existing autonomous vehicle systems use color to its full extent, largely because color-based recognition in outdoor scenes is complicated, and existing color machine-vision techniques have not been shown to be effective in realistic outdoor images. This paper presents a technique for achieving effective real-time color recognition in outdoor scenes. The technique uses multivariate decision trees for piecewise linear non-parametric function approximation to learn the color of a target object from training samples, and then detects targets by classifying pixels based on the approximated function. The method has been successfully tested in several domains, such as autonomous highway navigation, off-road navigation and target detection for unmanned military vehicles, in projects such as the U.S. National Automated Highway System (AHS) and the U.S. Defense Advanced Project Agency — Unmanned Ground Vehicle (DARPA-UGV). MDT-based systems have been used in stand-alone mode, as well as in conjunction with systems based on other sensor configurations.

Safety and capacity analysis of automated and manual highway systems

This paper compares safety of automated and manual highway systems with respect to resulting rear-end collision frequency and severity. Safety is related to driver, vehicle and highway operating characteristics. Our safety analysis method maps the variation in these operating characteristics, modeled by probability distributions, to the probability and severity of the first rear-end crash due to a hard braking disturbance on the highway. The results show that automated driving is safer than the most alert manual drivers, at similar speeds and capacities. We also present a detailed safety-capacity trade-off study for four different automated highway system concepts that differ in their information structure and separation policy. This study quantifies the impact of inter-vehicle cooperation and operating speed of the Automated Highway System (AHS). It also compares and contrasts the safety characteristics of individual vehicle and platoon based Automated Highway Systems.

Changing Lanes on Automated Highways with Look-Down Reference Systems

Lane change is a vital component of the steering control system for automated vehicles. Look-down system faces the challenge of having to bridge the gap between the references in the center of the respective lanes. This paper discusses two methods that were employed in the platoon demonstration of the National Automated Highway Systems Consortium: infrastructure guided lane changes using cross-over references and free lane changes using dead-reckoning. Similar techniques were applied to steering control on entrance and exit ramps of automated highways.

Microscopic Simulation Analysis for Automated Highway System Merging Process

The automated highway system (AHS) concept with dedicated lanes is not designed as a stand-alone transportation facility. Drivers will by necessity need to drive from their origins to the AHS entrance and from the AHS exit to their final destinations. Therefore, the AHS will affect other transportation facilities and will need to be integrated with all other facilities in the transportation system. Interfaces create much of the congestion for today’s transportation systems. AHS interfaces may cause similar problems, as a result of either AHS interactions with conventional systems or internal limitations from AHS merging capabilities. If these problems exist, either the AHS or the conventional road network cannot function properly. Then the system as a whole will break down, and the AHS could prove a detriment to the overall transportation system. Clearly not enough is known about the automated merging process to determine what conditions would lead to congestion at interface points. Current macroscopic techniques assume parameters that are not applicable to an AHS, and no detailed AHS merging models have been developed and validated. The AHS to conventional roadway interface problem is addressed by presenting a microscopic simulation model for one scenario of the automated merging maneuver. Some numerical results are presented for this merging scenario.

Technological Challenges In the Development of AHS

The objective of an Automated Highway System (AHS) is to enhance user comfort, convenience and safety with vehicle and highway automation. In a broad sense vehicle and highway automation has been an ongoing process with many improvements in vehicles and infrastructure introduced over the years, such as vehicle cruise control and roadway traffic signal sequence control. In a narrower definition, the introduction of vehicle and highway automation will reduce the role of drivers to various degrees. The development of an AHS is likely to be controversial for many years and will have far-reaching ripple effects. The AHS is very influential since it relates closely to the daily lives of people. Although it may become only an optional type of transportation, the success of the AHS development can cause significant changes in the way people travel. In this paper, we discuss the technical aspects of vehicle and highway automation for an AHS and will try to identify the critical challenges to bring an AHS into reality. Although the concepts of an AHS are still being debated and the implementation of a national AHS is not imminent, it is timely and beneficial to examine the technological elements, to explore the current limitations and to identify the hurdles yet to overcome.

Axiomatic Approach To Developing Partial Automation Concepts for Deployment of Automated Highway Systems and Partial Invocation of Vision-Based Lane-Keeping and Adaptive Cruise Control

Discussions about the pros and cons of the automated highway system (AHS) visions are nothing but intellectual exercises unless the issue of how to evolve the current highway system toward this end state can be resolved. The primary motivation for the AHS is its potential for considerable highway capacity gain without major acquisition of right-of-way. Many believe that such capacity gain is possible only when lanes are dedicated to the use of those vehicles equipped for full automation. However, to avoid the empty-lane syndrome, there must exist a sufficient population of automation-equipped vehicles that can use the dedicated lane at once or shortly thereafter. Also, if such automation-equipped vehicles can be used only on such dedicated lanes, few people would purchase such vehicles before dedication of lanes on a network basis, the well-known “chicken-and-egg” problem. In this paper partial-automation concepts are proposed that help solve this chicken-and-egg problem. Because of the futuristic nature of the AHS, many technological and nontechnological questions cannot be answered definitely. Assumptions must first be made about the likely or reasonable answers to such questions and then requirements derived for partial-automation concepts based on these assumptions. The goal is for the inferencing process to be rigorous and correct so that only the assumptions are to be debated. The author believes that the assumptions made are reasonable and therefore that the requirements for partial-automation concepts and the actual partial-automation concepts proposed are necessary. Most important, it is hoped that this approach will facilitate a more rigorous process in exchanging ideas and debating AHS deployment issues.

Functional Evolution of Automated Highway System for Incremental Deployment

A combination of market forces, cost constraints, and other factors necessitates incremental evolution of a fully automated highway system (AHS) rather than instantaneous deployment. Thus, an understanding of the interdependencies among required AHS functional capabilities is essential for planning. In this paper a set of three AHS functional evolution reference models is proposed that include essential as well as supplemental functions. The reference models include lateral motion handling, longitudinal motion handling, obstacle handling, and selected infrastructure support functions. This family of three models is used to present the needs of baseline autonomous tactical vehicle operation, the benefits of adding inter-vehicle communications, and the benefits of adding infrastructure support. The reference models reveal a critical need for vehicle motion prediction capability and suggest that both communications and infrastructure support are beneficial but not mandatory for achieving an AHS. Furthermore, there appear to be a number of safety and efficiency benefits that can be realized with only partial automation and in some cases no automation. These results could help set priorities and guide strategies for incremental introduction of AHS technology into vehicles and roadways.

Orthogonal Capability Building Blocks for Flexible AHS Deployment

Once a baseline level of full automation is possible for an Automated Highway System (AHS), there are numerous choices to be made in deploying enhanced capabilities to improve safely, throughput, and travel time. Identifying a set of orthogonal capabilities enables describing multiple deployment paths within a common framework. Sixteen AHS configurations can be formed from a proposed set of orthogonal capabilities including: number of vehicles grouped into an entity (free agent vs. platoon), number of automated lanes (single or multiple), obstacle strategy (exclusion or detection), and system vigilance (trusting or vigilant). Given these capabilities, this systematic approach reveals a maximally enhanced end-slate configuration: a platooned, multi-lane, obstacle detecting, vigilant AHS that could be attained using any of 24 incremental deployment paths. A mapping technique is presented that can assist in risk management by depicting alternative deployment paths and constraints within a single framework.

Automated Highway System Field Operational Tests: Potential Sites, Configurations, and Characteristics

In 2002 the National Automated Highway System Consortium (NAHSC) is scheduled to complete its work on development of an automated highway system prototype. Upon completion of its mission, NAHSC is likely to be followed by one or more field operational tests (FOTs) in which ordinary drivers will use automated vehicles on a real roadway under test conditions. Described are objectives for such a test, potential test sites in California, and the merits of these sites for conducting different types of tests. The evaluation is based on interviews with local officials, visits to 14 sites around the state, and collection of detailed data on these highways. It is concluded that there exist many potential FOT sites provided that the federal government pays for a large portion of infrastructure costs and that the new infrastructure is turned over to local agencies upon completion of the test.

Intermediate Automation Concepts for Incremental Deployment of Automated Highway Systems

Automated highway systems (AHS) are a promising concept whose implementation needs to take place in a modular and incremental manner. Immediate implementation of a fully automated highway system may not be feasible or desirable. It does not allow for the necessary testing and evolution of technology, markets, and social change. Recognizing the importance and challenge of progressive, evolutionary AHS deployment, six deployment assumptions are presented, three deployment issues are discussed, and several intermediate automation concepts for evolution toward AHS are proposed. Concepts are presented in the form of “market packages.” Some of these concepts are simple driver aiding systems; others are capable of supporting hands-off and feet-off driving. In the evolutionary path to AHS, a number of comfort and safety enhancements could be realized initially without large infrastructure modifications and without dedicated lanes. Intermediate deployment steps are necessary to help early deployment of partial automation, to allow AHS technology to mature, to establish user confidence, and to create market demand and public acceptance. The packages presented are designed so that they attract the driving public with comfort and safety benefits while requiring no significant roadway infrastructure modification and they encourage motorists to purchase (or retrofit) vehicles with equipment that enables hands-off and feet-off driving, thus building confidence in and creating demand for AHS.

Human Factors Issues for Automated Highway Systems

The automated highway system (AHS) is “the application of vehicle/highway automation technology to provide significant improvements in traffic safety, throughput, travel times, comfort, convenience, energy, and [the] environment.” Under a contract with the Federal Highway Administration to investigate human factors aspects of the design of the AHS, 14 experiments and several analytical tasks have been conducted. The results of the experiments and analytical work on automated-steering failures are reviewed, followed by a summary of the implications of that work for automated highway systems. Then, several critical human factors research issues - from a list of 62 developed during the contract - are presented and discussed.

Capacity Analysis of Traffic Flow Over a Single-Lane Automated Highway System☆

We calculate bounds on per-lane Automated Highway System (AHS) capacity as a function of vehicle capabilities and control system information structure. We assume that the AHS lane is dedicated for use by fully automated vehicles. Capacity is constrained by the minimum inter-vehicle separation necessary for safe operation. A methodology for deriving the safe minimum inter-vehicle separation for a particular safety criterion is presented. The inter-vehicle separation, which depends on the vehicle braking capability, control loop delays and operating speed, is then used to compute site-independent upper bounds on AHS capacity for a given mix of vehicle classes. The sensitivity of the capacity with respect to the degree of inter-vehicle cooperation, check-in policies (governing minimum acceptable vehicle-braking capability), highway speed limits, and lane-use policies (governing the sharing of a lane by multiple vehicle classes) is also investigated.

Why We Should Develop a Truly Automated Highway System

The reasons in favor of developing an automated highway system (AHS) are addressed. The anticipated benefits in highway capacity increases, travel time reductions, safety improvements, reduction of driving stress and tedium, elimination of adverse driving behavior, alternative uses of traveling time, more predictable travel time, and reduction of exhaust emissions and energy consumption are reviewed. The concerns that have been raised by those who are skeptical of AHS are then reviewed, indicating which have already been addressed and which remain subject to continuing uncertainty and research.

The automated highway system: A transportation technology for the 21st century

The current vehicle-highway system has reached a plateau in its ability to meet the demand for moving goods and people. This paper sketches an architecture for an automated highway system or AHS. The architecture can be realized by several designs that differ in terms of performance and sophistication. One design is described that could triple capacity and reduce travel time, guarantee collision-free operation in the absence of malfunctions, limit performance degradation in the case of faults, and reduce emissions by half. Evidence suggesting that the design can be implemented is summarized. It is indicated how the design can be adapted to different urban and rural scenarios and how a standard land-use model can show the impact of AHS on urban density. A summary of the progress of the National Automated Highway Systems Consortium is provided. The paper concludes with a critique of AHS.

A survey of present ivhs activities in Japan

The Japanese Government has been conducting IVHS (Intelligent Vehicle-Highway Systems) projects on ATMS (Advanced Traffic Management Systems), ATIS (Advanced Traveller Information Systems) and AVCS (Advanced Vehicle Control Systems). In the spring of 1996, VICS (Vehicle Information and Communication System) started a driver information service including dynamic route guidance, and ASV (Advanced Safety Vehicle) aiming at active safety for passenger cars had demonstrations. Experiments related to Automated Highway Systems have been conducted since 1995 on a test track and an expressway. Cooperative driving, with inter-vehicle communication, was tested in the spring of 1997. Besides the Government projects, navigation systems have become widespread, and inter-vehicle distance warning systems for trucks and an intelligent cruise control system for passenger cars have become commercially available.