Describes the design of an automated highway system (AHS) developed over the past ten years in the California PATH program. The AHS is a large, complex system, in which vehicles are automatically controlled. The design and implementation of the AHS required advances in actuator and sensor technologies, as well as the design, analysis, simulation, and testing of large-scale, hierarchical hybrid control systems. The paper focuses on the multilayer AHS control architecture and some questions of implementation. It discusses in detail the design and safety verification of the on-board vehicle control system and the design of the link-layer traffic-flow controller.

Control design of an automated highway system

One of the riskiest maneuvers that a driver has to perform in a conventional highway system is to merge into the traffic and/or to perform a lane changing maneuver. Lane changing/merging collisions are responsible for one-tenth of all crash-caused traffic delays often resulting in congestion. Traffic delays and congestion, in general, increase travel time and have a negative economic impart. We analyze the kinematics of the vehicles involved in a lane changing/merging maneuver, and study the conditions under which lane changing/merging crashes can be avoided. That is, given a particular lane change/merge scenario, we calculate the minimum longitudinal spacing which the vehicles involved should initially have so that no collision, of any type, takes place during the maneuver. Simulations of a number of examples of lane changing maneuvers are used to demonstrate the results. The results of this paper could be used to assess the safety of lane changing maneuvers and provide warnings or take evasive actions to avoid collision when combined with appropriate hardware on board of vehicles.

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Collision avoidance analysis for lane changing and merging

CALIFORNIA PATH PROGRAM INSTITUTE OF TRANSPORTATION STUDIES UNIVERSITY OF CALIFORNIA, BERKELEY Collision Avoidance Analysis for Lane Changing and Merging Hossein Jula, Elias B. Kosmatopoulos, Petros A. Ioannou University of Southern California California PATH Research Report UCB-ITS-PRR-99-13 This work was performed as part of the California PATH Program of the University of California, in cooperation with the State of California Business, Transportation, and Housing Agency, Department of Transportation; and the United States Department of Transportation, Federal Highway Administration. The contents of this report reflect the views of the authors who are responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the State of California. This report does not constitute a standard, specification, or regulation. Report for MOU 317 May 1999 ISSN 1055-1425 CALIFORNIA PARTNERS FOR ADVANCED TRANSIT AND HIGHWAYS

Collision Avoidance Analysis for Lane Changing and Merging

The projected rapid growth of the market penetration of connected and autonomous vehicle technologies (CAV) highlights the need for preparing sufficient highway capacity for a mixed traffic environment where a portion of vehicles are CAVs and the remaining are human-driven vehicles (HVs). This study proposes an analytical capacity model for highway mixed traffic based on a Markov chain representation of spatial distribution of heterogeneous and stochastic headways. This model captures not only the full spectrum of CAV market penetration rates but also all possible values of CAV platooning intensities that largely affect the spatial distribution of different headway types. Numerical experiments verify that this analytical model accurately quantifies the corresponding mixed traffic capacity at various settings. This analytical model allows for examination of the impact of different CAV technology scenarios on mixed traffic capacity. We identify sufficient and necessary conditions for the mixed traffic capacity to increase (or decrease) with CAV market penetration rate and platooning intensity. These theoretical results caution scholars not to take CAVs as a sure means of increasing highway capacity for granted but rather to quantitatively analyze the actual headway settings before drawing any qualitative conclusion. This analytical framework further enables us to build a compact lane management model to efficiently determine the optimal number of dedicated CAV lanes to maximize mixed traffic throughput of a multi-lane highway segment. This optimization model addresses varying demand levels, market penetration rates, platooning intensities and technology scenarios. The model structure is examined from a theoretical perspective and an analytical approach is identified to solve the optimal CAV lane number at certain common headway settings. Numerical analyses illustrate the application of this lane management model and draw insights into how the key parameters affect the optimal CAV lane solution and the corresponding optimal capacity. This model can serve as a useful and simple decision tool for near future CAV lane management.

A mixed traffic capacity analysis and lane management model for connected automated vehicles: A Markov chain method

Several automobile manufacturers are offering assisted driving systems that use sensors to automatically brake automobiles to avoid collisions. Before extensively deploying these systems, we should determine how they will affect highway capacity. The goal of this paper is to compare the highway capacity when using sensors alone and when using sensors and vehicle-to-vehicle communication. To achieve this goal, the rules for using both technologies to prevent collisions are proposed, and highway capacity is estimated based on these rules. We show that both technologies can increase highway capacity. The increase in capacity is a function of the fraction of the vehicles that use a technology. If all of the vehicles use sensors alone, the increase in highway capacity is about 43%. While if all of the vehicles use both sensors and vehicle-to-vehicle communication, the increase is about 273%.

Highway Capacity Benefits from Using Vehicle-to-Vehicle Communication and Sensors for Collision Avoidance

The inter-vehicle separation during vehicle following is one of the most critical parameters of the automated highway system (AHS), as it affects both safety and highway capacity. The trade-off between capacity and safety gives rise to a variety of different AHS concepts and architectures. In this study we consider a family of AHS operational concepts. For each concept we calculate the minimum inter-vehicle spacing that could be used for collision-free vehicle following, under different road conditions. For architectures involving platoons we also use the alternative constraint of bounded energy collisions to calculate the minimum spacing that can be applied if we allowed collisions at a limited relative velocity in case of emergency stopping. The minimum spacing is used to calculate the maximum possible capacity that could be achieved for each operational concept.

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Spacing and capacity evaluations for different AHS concepts

In this study, the authors consider a family of six Automated Highway Systems (AHS) operational concepts. For each concept, the minimum inter- vehicle spacing that could be used for collision-free vehicle following, under different road conditions, is calculated. For architectures involving platoons, the authors also use the alternative constraint of bounded energy collisions to calculate the spacing that can be applied if collisions at a limited relative velocity were allowed. In every case, the minimum spacing in turn, is used to calculate the maximum possible capacity that could be achieved for each operational concept.

Spacing And Capacity Evaluations For Different Ahs Concepts

This document is Volume IV of the final report on precursor systems analyses of the Automated Highway System (AHS). It analyzes the requirements, issues, and risks associated with lateral and longitudinal control of vehicles operating on the AHS. This report presents a possible evolutionary path for the automation of lateral and longitudinal control. This evolutionary path is characterized by five evolutionary representative system configurations (ERSCs). This analysis looks at the development of longitudinal, lateral and finally combined lateral and longitudinal systems in terms of the performance and reliability requirements and deployment scenarios. The performance requirement analysis covers driver comfort and acceptance issues during automatic control and transitions between automatic and manual control in addition to investigating the sensor, actuator and controller requirements for the control systems. Roadway traffic controllers may improve traffic flow through traffic networks in terms of travel time reduction and congestion avoidance. The reliability requirements analysis uses NHTSA's accident rates data to quantify the reliability requirements in various levels of vehicle automation. This report derives the reliability functional requirements for the automatic systems used in lateral and longitudinal control. The reliability functional requirements allow us to assess the required redundancy and structural complexity in implementing these automatic systems. This information can be used to estimate the cost and difficulty to build the automated highway systems.

Precursor systems analyses of automated highway system. final report. volume iv: lateral and longitudinal control analysis

This documentation and software provides a tool which enable a user to perform the following tasks regarding vehicle spacing: calculate the minimum initial spacing between two vehicles, calculate the possibility and severity of collision between two vehicles, visualize the motion of the two vehicles in the longitudinal direction during braking maneuvers, and calculate the highway capacity given factors for velocity, spacing, and size of vehicles and platoons.

Alexander Kanaris

Papers

Spacing and capacity evaluations for different AHS concepts

Spacing And Capacity Evaluations For Different Ahs Concepts

Spacing And Capacity Evaluations For Different Ahs Concepts

Precursor systems analyses of automated highway system. final report. volume iv: lateral and longitudinal control analysis

Inter Vehicle Spacing: User’s Manual