Showing papers on "Intelligent transportation system published in 1995"

Global positioning systems in the time domain: How useful a tool for intelligent vehicle-highway systems?

Abstract: Much of the research and development work in intelligent vehicle-highway systems (IVHS) relies on the availability of methods for locating and monitoring vehicles (e.g. “probe vehicles”) in real time across a road network. This paper considers the use of the global positioning system (GPS) as one method for obtaining information on the position, speed and direction of travel of vehicles. It reports the results of a series of field studies, in which real-time GPS data were compared to data collected by an instrumented vehicle, under a range of physical and traffic conditions. The field studies and consequent data analysis provide a picture of the reliability and usefulness of GPS data for traffic monitoring purposes, and hence the possibilities for the use of GPS in IVHS projects. The use of GPS receivers tailored for mobile applications, and able to provide direct observations of vehicle speed and travel direction, coupled with database management using geographic information systems (GIS) software, was found to provide a reliable and efficient system for vehicle monitoring. Field data collection under “ideal” GPS conditions indicated that accurate speed and position data were readily obtained from the GPS. Under less favourable conditions (e.g. in downtown networks), data accuracy decreased but useful information could still be obtained. In addition, the conditions and situations under which GPS data errors could be expected were noted. The finding that it is possible to relate standard GPS signal quality indicators to increased errors in speed and position provides an enhanced degree of confidence in the use of the GPS system for real-time traffic observations.

Probe vehicle sample sizes for real-time information: the Houston experience

Abstract: Probe vehicle travel time data is an important source of real-time travel information for a variety of intelligent transportation system applications This paper investigates the required minimum number of probe vehicles that are necessary to report real-time travel speeds and times for a desired statistical accuracy Empirical travel time data from the Houston traffic monitoring system were analyzed to calculate travel time variation and the corresponding minimum required probe vehicle sample sizes A regression equation was developed to estimate travel time variation, which can then be used to calculate sample sizes It was concluded that the current number of probe vehicles in Houston provide reliable peak period travel speed information (ie, 95% confidence that displayed real-time speeds are /spl plusmn/10%)

Intelligent control for autonomous systems

Abstract: Intelligent control is the discipline in which control algorithms are developed by emulating certain characteristics of intelligent biological systems. It is quickly emerging as a technology that may open avenues for significant advances in many areas. In fact, fueled by advancements in computing technology, it has already achieved some very exciting and promising results. Here, the author argues that a mixture of intelligent and conventional control methods may be the best way to implement autonomous control systems. >

Development of advanced traffic signal control strategies for intelligent transportation systems: multilevel design

Abstract: The development of advanced traffic signal control strategies suitable for advanced traffic management within Intelligent Transportation Systems is described. The strategies consist of a multilevel design for the real-time, traffic-adaptive control of an urban signal network. This design permits the system to be built up gradually to offer varying degrees of responsiveness, depending on particular network and traffic characteristics. The more advanced control levels in the hierarchy incorporate the capabilities of the lower control levels. A principal goal of the multilevel design is to invoke a selected control strategy when it can provide the greatest benefits and thus maximize the overall effectiveness of the system.

Solving an Instantaneous Dynamic User-Optimal Route Choice Model

Abstract: Dynamic models of the behavior of automobile drivers in choosing routes through urban transportation networks are required for the design and operation of intelligent transportation systems generally, and traveler information systems in particular. In this paper, drivers' route choice behavior based on current, or instantaneous, information on network conditions is described using an optimal control theory formulation. The time-dependent origin-destination vehicle trip pattern is assumed to be known. The instantaneous dynamic user-optimal route choice problem is to allocate vehicle flows to the current minimal-cost routes, defined as the routes that minimize the route travel cost between each decision node (any node on the route including the origin) and the destination node based on the currently prevailing travel times. The continuous time formulation of the problem is transformed into a discrete time nonlinear programming (NLP) formulation. Each of a sequence of NLPs is then solved by an algorithm base...

Hierarchical Hybrid Control: A Case Study

Abstract: A case study of the difficulties encountered in the design of hierarchical, hybrid control systems is presented. As our example we use the Intelligent Vehicle Highway System (IVHS) architecture proposed for vehicle platooning, a system that involves both continuous state and discrete event controllers. We point out that even though conventional analysis tools suggest that the proposed design should fulfill certain performance requirements, simulation results show that it does not. We consider this as an indication that the conventional tools currently in use for the design and verification of control systems may be inadequate for the design of hierarchical controllers for hybrid systems. The analysis also indicates certain shortcomings of the current IVHS design. We propose solutions to fix these problems.

A comparison of system optimum and user equilibrium dynamic traffic assignments with schedule delays

Abstract: One way to estimate the potential benefits of new traffic control and management systems is to compare the total cost incurred in equilibrium with the system optimized total cost. To do this, we formulate the dynamic traffic assignment models with schedule delays under the system optimum and user equilibrium principles and solve them using numerical methods. System optimum and user equilibrium dynamic assignments on an 18-arc test network are then compared in terms of total travel times and schedule delays at different levels of traffic congestion. This comparison provides important implications for the success of the intelligent transportation systems (ITS) in reducing traffic congestion.

A Broader Context for Transportation Planning: Not Just An End In Itself

Abstract: The end of the Interstate era, marked by the passage of the Intermodal Surface Transportation Efficiency Act (ISTEA), signaled a move toward healthy and sustainable transportation systems. This article explains the philosophy that led planners to vast, but separate, transportation systems and the proposed changes in direction that will create a multi-modal system that is flexible and encompasses environmental and social concerns. Transportation goals that support a sustainable society as well as goals of a sustainable transportation system are listed. New investment strategies will begin with planning and end with the incorporation of economic, social, and environmental factors. Governments will seek out and involve interest groups to set priorities, shifting attention from mobility to accessibility.

Development of an intelligent cruise control system

Abstract: An intelligent cruise control system has been developed. The system consists of cruise control and headway distance warning functions. This paper describes the sensing system, the control algorithm, and the system effectiveness evaluated by various vehicle tests. The system consists of vehicle sensors, a laser radar and video camera that recognizes preceding vehicles, a controller, a throttle actuator, and automatic transmission, etc. The scanning type laser radar detects the distance and direction to the target object by measuring the elapsed time between emission of pulse beam and reception of reflected beam. The video camera is used to recognize the current traveling lane. The forward view road image obtained with the camera is processed and the lane boundaries are extracted with the edge extraction technique. When the vehicle is running on cruise control mode, the system adjusts engine output or transmission shift so as to maintain the headway distance, and issues a warning when approaching too close to a preceding vehicle. The operation switches for intelligent cruise control are the same as those for the conventional cruise control system. The center message display provides system operation status, such as set speed, headway distance, control status, and warning. The effectiveness of the intelligent cruise control in providing safe and comfortable driving was verified by various field tests.

Statistical analysis of commercial driver and dispatcher requirements for advanced traveler information systems

Abstract: This paper analyzes the responses from two nationwide surveys designed to obtain user information requirements for the design of advanced traveler information systems (ATIS) and commercial vehicle operations (CVO) with respect to commercial system operators (dispatchers) and commercial vehicle drivers. A total of 673 returned surveys (348 dispatcher surveys and 325 commercial driver surveys), were used in the analysis. Mathematical models were developed, using a binomial logit to predict whether the commercial driver or dispatcher would use an intelligent transportation system, and an ordered probit to estimate the importance of information (i.e. route and navigation, roadside services, personal communication and road and traffic information) to be provided by in-vehicle information systems. The results of this study provide guidelines for the design of information systems and help define informational requirements for users of ATIS/CVO.

A decentralized scheme for real-time route guidance in vehicular traffic networks

Abstract: Real-time route guidance is one of the fundamental capabilities offered by advanced traveler information systems (ATIS). ATIS supports advanced traveler management systems to assist trip makers in avoiding congestion by en-route diversion messages to enhance individual convenience and improve the system's efficiency. This paper describes ongoing work at the University of Texas at Austin to develop a procedure for real-time route guidance in congested vehicular traffic networks. The control procedure, implementable in a decentralized architecture, is designed to offer flexibility and robustness in dealing with various knowledge available. The decentralized approach envisions a set of local controllers scattered or distributed in the network, where every controller can only extract limited "raw" information from network detectors, and utilizes this information to guide the within-territory vehicles to their individual destinations. The assignment procedure is driven by informed local search procedure with heuristics. The structure of the control procedure is designed to allow communication among various controllers to enrich the level of knowledge and to obtain decisions. A simulation-assignment model is developed to assess the effectiveness of the proposed architecture. A comparative study was undertaken to gauge the performance of the local structure against a benchmark scenario of time-dependent system optimal logic in a centralized architecture. The assessment was conducted under different network structure, loading patterns, heuristics, and knowledge levels. The results obtained to date have been very encouraging regarding the performance of this partially-informed decentralized approach relative to fully-informed centrally coordinated procedures that require considerably more information and computer processing resources.

A framework for intelligent sensor validation, sensor fusion, and supervisory control of automated vehicles in ivhs

Abstract: This paper proposes a framework for real-time monitoring and diagnosis of automated vehicles in an intelligent vehicle-highway system (IVHS) environment. The supervisory control methodology proposed here is concerned with fault detection, fault isolation, and control reconfiguration of the many sensors, actuators, and controllers used in the control process. This supervisory control architecture operates at two levels of the automated vehicle-control system (AVCS) -- the regulation level and the coordination level. Supervisory control activities at the regulation level deal with validation and fusion of sensory data and with fault diagnosis of the actuators, sensors, and the vehicle itself. Supervisory control activities are achieved through five modules organized in an hierarchical manner. The paper presents an overview of the different methods being used to build such a supervisory controller.

Archisim: multi-actor parallel architecture for traffic simulation

Abstract: This paper presents a microscopic traffic simulation based on distributed architecture and on the concepts of multi-actors and multi-process. The information related to the network (topology, graph, and equipment) are considered available. In fact, they can be defined by using a graphic interface. The road objects occurring in this simulation are: the static objects, such as intersection and curve signs; the pseudo-static objects, such as flow sensors, traffic lights, and variable message signs; and the dynamic objects, such as vehicles and pedestrians. The dynamic objects also play a part as actors in the simulation. The last actor type is the intersection supervisor, which is in charge of a traffic lights group. The software architecture adopted is distributed, multi-actor, and multiprocess. The actors occurring in the simulation are: vehicles, pedestrians, and intersection supervisors. The processes simulated are: the road network manager, the vehicles, the pedestrians, and the intersection supervision. The network manager is the main process and has the global knowledge of the network. There is no direct communication link between the actors. The actors communicate only with the network manager process. At each communication, vehicle and pedestrian actors send to the network manager their location and their characteristics and ask it for their local vision; the intersection supervisor sends the color lights and asks for the contents of some specified flow sensors. The road network manager updates the graph. This parallel architecture can be used not only for a microscopic simulation but it can be connected to a piloted simulator; in this case it plays the part of traffic generator where the simulated vehicles react to the pilot actions.

Public transport information systems in munich

Abstract: Passenger information is seen as an important medium to enhance public transport patronage. This is documented by a number of advanced transport telematics (ATT) applications in Europe. The philosophy within the public transport network in the Munich area, served by the Munich Public Transport Association, is to offer transport chains with optimal transfer conditions. But in a dense network of different transport systems, it is difficult to find the best way. Advanced timetable information systems can help passengers before and during their trips. Real-time operation data of all transport means help the operator to improve his service and give reliable information to passengers. Automatic vehicle monitoring (AVM) is used for dynamic schedule synchronization to guarantee transfer connections. To manage the relevant public transport data for information of operators and passengers, a public transport data center (PTDC) was developed, which integrates the control centers for tram/bus, underground, and S-Bahn having operated independently in the past. The PTDC provides the different information systems with up-to-the-minute data on current operation. In Munich, the main system also for real-time information is the electronic timetable information system, which has been upgraded to a dynamic version. Accurate information is now available in inquiry offices, at public touch screen terminals, and at home or on private personal computers via phone connections using a modem or a radio interface. Other information systems supplied by the PTDC are the PT transfer control and information systems for car drivers, such as variable message signs in connection with park and ride, RDS/TMC, and the dynamic route guidance system, EURO-SCOUT. For real-time passenger information at stops, display units using a new technology cheaper than LCD and LED are tested. The main innovations are the integration of several systems, dynamic timetable information, and automatic schedule synchronization.

A route based variant of the aimsun2 microsimulation model

Abstract: AIMSUN2 is a combined discrete-continuous simulator of road traffic. It can represent elements of the road system that change continuously during the simulation period as well as elements that change at discrete time intervals. AIMSUN2 is a microscopic road traffic simulator that models individual vehicles and their driver behavior. It distinguishes between different types of vehicles and drivers. AIMSUN2 also handles a variety of network geometries and can represent incidents, conflicting maneuvers, and so on. The purpose of this paper is to present a variant of AIMSUN2 that considers explicitly origin-destination matrices and the routes selected, and possibly modified, due to information that becomes available while the simulated trip is taking place. This new feature of the microsimulation model makes it suitable for application for a variety of intelligent transportation systems (ITS) applications that are related to temporal, time dependent route choice behavior by several classes of drivers. The results obtained with this variant of AIMSUN2 are illustrated in several pilot applications that demonstrate its suitability for temporal route choice simulation. The ouputs provided by AIMSUN2 include a continuous animated graphical representation of the traffic network performance, the reporting of various statistics, and enhanced data gathered by simulated detectors with the route information followed by each simulated vehicle with "within day" and day to day" modifications.

A parameter identification of a car-following model

Abstract: It has been observed on Japanese motorways recently that traffic congestion occurs at bottlenecks, such as sags and tunnels on uninterrupted sections. These bottleneck phenomena have not been studied in detail partly because of the difficulty in acquisition of observed data from real traffic flow. In order to study the bottleneck phenomenon and car-following behavior on sags, an observation is made using a kite balloon at a sag bottleneck on Tomei Expressway. Parameter identification of a new car-following model suggested by Koshi is conducted using the observed data for each vehicle by the kite balloon. The identification is formulated for each observed vehicle by an output error least squares method (OELS) in terms of output errors in spacing and speed, and is solved through a complex search algorithm. It is found that the OELS formulation using the performance of spacing gives better results than that using speed. Both simulated speed and spacing are close to the observed data using the estimated parameters of the car-following model. The car-following model is found to be able to simulate the real traffic flow to a certain acceptable extent through the car-following simulation. Parameter analyses including probabilistic distribution and sensitivity for each parameter of the model are also discussed.

The electronic motorist

Abstract: The shortcomings of the human driver are getting help from emerging technologies in the guise of navigation systems, engine immobilizers, night vision assistance, automated collision alert, air bag systems, low tyre pressure warning system, and fuzzy logic. The author describes these technologies. In particular the author describes some of the LCD display navigation systems, and intelligent transportation systems, including vehicle location, of which navigation is a component. >

Wireless Communications For Intelligent Transportation Systems

Abstract: The ultimate selection of particular mobile communications systems will greatly affect the viability of any Intelligent Transportation Systems (ITS) network, so this decision must be based on a clear understanding of the costs and other performance parameters of the various technologies available. This book is the result of a comprehensive literature review of wireless communications technologies. The review has been supplemented with personal interviews conducted with industry representatives and Department of Transportation officials. As the research progressed, the leading wireless technologies selected for detailed evaluation were identified: cellular telephony, personal communications services, cordless telephony, radiopaging, private land mobile radio, radio data networks, wireless local area networks, terrestrial microwave relay, satellites, and meteor burst.

Intelligent transportation system Mayday becomes a reality

Abstract: The Intelligent Transportation System (ITS) is envisioned as linking existing and emerging technologies of computers, wireless radio communications systems, and various sophisticated sensors to be used in cars and highways to create an integrated system that has the potential to change the way millions of American. In Colorado, a large scale operational test of an ITS Mayday emergency dispatch system has been launched. This Mayday operational test in Colorado is evaluating the use of GPS location technology and cellular phone two-way communications to provide assistance to travelers in an emergency dispatch area of more than 12,000 square miles in central Colorado. The test implements 2,000 in-vehicle units using a low cost GPS location device called the TIDGET, developed by NAVSYS Corporation. The major objectives of the Colorado test are: to evaluate the impact of the system and response network on emergency response activities, time, and public safety; to evaluate a low cost system that allows user to request roadside assistance; and to identify the necessary structure, responsibilities, and service levels of a Travel Assistance Center for commercial operation of the system. The results of this emergency location project are anticipated to make a significant contribution to increased highway traveler safety and reduced emergency response time. This NAVSYS Mayday system is an example of the rapid progress by which the ITS vision is becoming a reality in today's travel technology.

Autoalert: automated acoustic detection of incidents

Abstract: This Innovations Deserving Exploratory Analysis (IDEA) project included the design and preliminary evaluation, as well as feasibility demonstration, of AutoAlert, an acoustic traffic sensor system that applies new signal processing algorithms to passive acoustic data to advance the state of practical acoustic incident detection techniques. These techniques, originally developed for national defense applications, will perform reliable, automatic, nearly instantaneous, all-weather incident detection under highly variable traffic conditions. Effective operation of urban high-capacity Intelligent Transportation Systems (ITS) requires speedy detection of incidents at chokepoints, such as tunnels, bridges and other aerial structures, and dense urban arterials. AutoAlert overcomes shortcomings of loop and video detectors, such as their inability to distinguish between incidents and congestion, and the need for a human-in-the-loop for video detection. The AutoAlert processor "hears" an incident before congestion builds, and can be used either as an independent detector, or its outputs can be combined (data fusion) with other detector outputs for joint improved decisions and incident verification. AutoAlert algorithms will provide a new level of incident detection timeliness and reliability (low false alarms) by applying sophisticated statistical models: Hidden Markov Models and Canonical Variates Analysis. These are used to analyze both short-term and time-varying signals that characterize incidents.

Educating the new transportation professional

Abstract: The world of transportation is witnessing exciting and dramatic changes. These changes suggest the need for many organizations to reinvent themselves. The author proposes that academia put its own house in order by attracting new colleagues into transportation education through research programs like those for Intelligent Transportation Systems (ITS). The "New Transportation Professional", the author argues, will need a much broader and deeper education to participate effectively in transportation.

Intelligent driver support

Abstract: Increasing road traffic has lead to a large increase in accidents and congestion throughout the world. Traditionally, congestion problems have been alleviated by building more roads. This option, however, is now severely constrained due to lack of lane, environmental concerns, and the high cost of road construction. The intelligent driver support system, developed at Lucas, consists of a number of automatic systems, on a Jaguar car, that allow intelligent cruise control, collision avoidance, and lane support. These systems offer the driver greater safety and comfort, and if used widely, could drastically improve the efficiency of the existing road network. This paper describes the technology and shows results from the car's use on public motorways.