Intelligent Transportation Systems (ITS) implementations across the United States have been succe... more Intelligent Transportation Systems (ITS) implementations across the United States have been successful in reducing congestion, enhancing safety, and improving network performance. To help promote the vision of an integrated planning framework and provide project-level support for professionals developing alternatives that include ITS technologies, the Virginia Department of Transportation Northern Region Operations has developed and deployed a ITS Solutions Decision Support Tool. The tool centralizes and condenses ITS data into a more readily accessible format to facilitate prescribing ITS Solutions to applicable transportation problems. Users may search the decision tree by problem and need to identify suitable ITS Solutions or search alphabetically for one or more specific solutions. To help users assess different technologies, the tool generates a detailed report for an individual ITS Solution or a comparison report across multiple ITS Solutions. A separate administration tool is...
Transportation Research Record: Journal of the Transportation Research Board, 1998
One of the greatest challenges in building an expert system is obtaining, representing, and progr... more One of the greatest challenges in building an expert system is obtaining, representing, and programming the knowledge base. As the size and scope of the problem domain increases, knowledge acquisition and knowledge engineering become more challenging. Methods for knowledge acquisition and engineering for large-scale projects are investigated in this paper. The objective is to provide new insights as to how knowledge engineers play a role in defining the scope and purpose of expert systems and how traditional knowledge acquisition and engineering methods might be recast in cases where the expert system is a component within a larger scale client-server application targeting multiple users.
Transportation Research Part C: Emerging Technologies, 2001
... The computer provides traveler information to participants by emulating an IRANS capable of d... more ... The computer provides traveler information to participants by emulating an IRANS capable of displaying three ... During pre-trip planning players are shown a map of the network and asked to ... A general linear model (GLM) was estimated from data gathered during the first 10 trials ...
Merging the Transportation and Communications Revolutions. Abstracts for ITS America Seventh Annual Meeting and ExpositionITS America, 1997
This paper addresses aspects of the Advanced Traffic Management Systems and Advanced Traveler Inf... more This paper addresses aspects of the Advanced Traffic Management Systems and Advanced Traveler Information Systems (ATMS/ATIS) strategies and gives examples of recommended treatments. The test method used in this work is simulation based, using stochastic assignment of destinations and multiple replications that could be applied equally well to mathematical programming formulations. The modeled demands and network are idealized and used as illustrations of valid statistical treatments that would also be applicable to Traffic Management Center (TMC) evaluation of field data. To address the problem of unrepresentative peak period performance, multiple simulation replications are used. The use of 20 multiple replications in simulation is analogous to a month of AM or PM peak period weekdays. Using field observations, a TMC's statistical sampling of performance measures by vehicle probes or roadway sensors might be used in place of the exhaustive sampling possible in a simulation model. When Monte Carlo simulation is applied to modeling of ATMS/ATIS strategies or formulations, appropriate statistical treatments must be applied in determining if alternative strategies actually are significantly different. These statistical treatments include single-factor analysis of variance for normally distributed results and nonparametric methods, such as the Kruskal-Wallis test, for maximum values that would not be normally distributed. Performance can be treated as having demand and supply components. In this paper the driver, or demand-side, is treated as having a trip-based orientation. The average, variance, and maximum values of trip time as performance measures are examined for their statistical treatment of significant differences. Also, an estimation of two standard deviations of mean trip time is used to augment maximum trip time comparisons among strategies. The demand-side trip oriented significance tests in simulations might be extended to the case of TMC field evaluations by using limited sampling of probe vehicles. The network, or supply-side, is examined primarily with respect to density on the critical arcs of the network. Network performance is designed to capture the critical dynamic states of the network's supply utilization over time. The maximum density conveys the worst conditions on any arc. The number of arc-minutes that density is above a critical free flow density conveys the duration of congested conditions. The number of density-arc-minutes that density is above a critical free flow density conveys a measure of total congestion. This density data can be made available for a TMC, as well as in simulation. An example is given of the use of the Kruskal-Wallis test statistic in finding significant differences in maximum densities for four routing strategies.
This paper presents an innovative approach to Advanced Traffic Management and Information Systems... more This paper presents an innovative approach to Advanced Traffic Management and Information Systems that integrates real-time supply- side network capacity management with demand-side dynamic route choice. In this approach, local network managers oversee and direct flows toward optimality and drivers autonomously select routes in- vehicle in a viable partnership. Simulation modeling of dynamic peak period demands is used to study trip and network performance under four scenarios. It is shown that a mixed strategy, termed Arc Metering and which incorporates metering of network arcs as a supply- side management strategy, provides significant savings in travel time while enabling the network to accommodate higher volumes of peak- flows.
This paper has been mechanically scanned. Some errors may have been inadvertently introduced. CAL... more This paper has been mechanically scanned. Some errors may have been inadvertently introduced. CALIFORNIA PATH PROGRAM
~s one of ten regmnal umts mandated by Congress and estabhshed m Fall 1988 to support research, e... more ~s one of ten regmnal umts mandated by Congress and estabhshed m Fall 1988 to support research, educataon, and tralmng m surface transportatmn The UC Center serves federal Regmn IX and is supported by matching grants from the U S Department of Transportatmn, the Cahforraa Department of Transportation (Caltrans), and the Umvers~ty Based on the Berkeley Campus, UCTC draws upon exxstang capablhtles and resources of the Instatutes of
It has been contended that in-laboratory experimentation with interactive microcomputer simulatio... more It has been contended that in-laboratory experimentation with interactive microcomputer simulation can substitute for the lack of real-world applications and provide a useful approach to data collection and driver behavior analysis. With the rapid development but limited real-world deployment of Advanced Traveler Information Systems, interactive simulation has quickly grown in popularity among researchers studying dynamic driver behavior. This paper discusses the development and implementation of FASTCARS (Freeway and Arterial Street Traffic Conflict Arousal and Resolution Simulator), an interactive microcomputer-based animated simulator designed for in-laboratory experimentation to assist in the estimation and calibration of predictive models of driver behavior under the influence of real-time information.
Optimally routing vehicles over time and space is a central theme within real-time traffic manage... more Optimally routing vehicles over time and space is a central theme within real-time traffic management. This paper explores the application of a distributed artificial intelligence multiagent system that uses principled negotiation to improve dynamic routing and traffic management within roadway networks. On the demand side vehicles of individual drivers are equipped with intelligent route guidance systems capable of seeking and acquiring knowledge and assisting the traveler in developing trip itineraries. Real-time control over the transportation network is accomplished through an agent-based distributed hierarchy of system operators. Traveler information is gathered and disseminated by information service providers. Through pre-trip and en-route principled negotiation between agents, network performance is enhanced from the point of view of both drivers and system operators. The paper also demonstrates how this view of traffic management complements and builds upon the National ITS...
Transportation Research Record: Journal of the Transportation Research Board, 1998
For a wide range of transportation network path search problems, the A* heuristic significantly r... more For a wide range of transportation network path search problems, the A* heuristic significantly reduces both search effort and running time when compared to basic label-setting algorithms. The motivation for this research was to determine if additional savings could be attained by further experimenting with refinements to the A* approach. We propose a best neighbor heuristic improvement to the A* algorithm that yields additional benefits by significantly reducing the search effort on sparse networks. The level of reduction in running time improves as the average outdegree of the network decreases and the number of paths sought increases.
Intelligent Transportation Systems (ITS) implementations across the United States have been succe... more Intelligent Transportation Systems (ITS) implementations across the United States have been successful in reducing congestion, enhancing safety, and improving network performance. To help promote the vision of an integrated planning framework and provide project-level support for professionals developing alternatives that include ITS technologies, the Virginia Department of Transportation Northern Region Operations has developed and deployed a ITS Solutions Decision Support Tool. The tool centralizes and condenses ITS data into a more readily accessible format to facilitate prescribing ITS Solutions to applicable transportation problems. Users may search the decision tree by problem and need to identify suitable ITS Solutions or search alphabetically for one or more specific solutions. To help users assess different technologies, the tool generates a detailed report for an individual ITS Solution or a comparison report across multiple ITS Solutions. A separate administration tool is...
Transportation Research Record: Journal of the Transportation Research Board, 1998
One of the greatest challenges in building an expert system is obtaining, representing, and progr... more One of the greatest challenges in building an expert system is obtaining, representing, and programming the knowledge base. As the size and scope of the problem domain increases, knowledge acquisition and knowledge engineering become more challenging. Methods for knowledge acquisition and engineering for large-scale projects are investigated in this paper. The objective is to provide new insights as to how knowledge engineers play a role in defining the scope and purpose of expert systems and how traditional knowledge acquisition and engineering methods might be recast in cases where the expert system is a component within a larger scale client-server application targeting multiple users.
Transportation Research Part C: Emerging Technologies, 2001
... The computer provides traveler information to participants by emulating an IRANS capable of d... more ... The computer provides traveler information to participants by emulating an IRANS capable of displaying three ... During pre-trip planning players are shown a map of the network and asked to ... A general linear model (GLM) was estimated from data gathered during the first 10 trials ...
Merging the Transportation and Communications Revolutions. Abstracts for ITS America Seventh Annual Meeting and ExpositionITS America, 1997
This paper addresses aspects of the Advanced Traffic Management Systems and Advanced Traveler Inf... more This paper addresses aspects of the Advanced Traffic Management Systems and Advanced Traveler Information Systems (ATMS/ATIS) strategies and gives examples of recommended treatments. The test method used in this work is simulation based, using stochastic assignment of destinations and multiple replications that could be applied equally well to mathematical programming formulations. The modeled demands and network are idealized and used as illustrations of valid statistical treatments that would also be applicable to Traffic Management Center (TMC) evaluation of field data. To address the problem of unrepresentative peak period performance, multiple simulation replications are used. The use of 20 multiple replications in simulation is analogous to a month of AM or PM peak period weekdays. Using field observations, a TMC's statistical sampling of performance measures by vehicle probes or roadway sensors might be used in place of the exhaustive sampling possible in a simulation model. When Monte Carlo simulation is applied to modeling of ATMS/ATIS strategies or formulations, appropriate statistical treatments must be applied in determining if alternative strategies actually are significantly different. These statistical treatments include single-factor analysis of variance for normally distributed results and nonparametric methods, such as the Kruskal-Wallis test, for maximum values that would not be normally distributed. Performance can be treated as having demand and supply components. In this paper the driver, or demand-side, is treated as having a trip-based orientation. The average, variance, and maximum values of trip time as performance measures are examined for their statistical treatment of significant differences. Also, an estimation of two standard deviations of mean trip time is used to augment maximum trip time comparisons among strategies. The demand-side trip oriented significance tests in simulations might be extended to the case of TMC field evaluations by using limited sampling of probe vehicles. The network, or supply-side, is examined primarily with respect to density on the critical arcs of the network. Network performance is designed to capture the critical dynamic states of the network's supply utilization over time. The maximum density conveys the worst conditions on any arc. The number of arc-minutes that density is above a critical free flow density conveys the duration of congested conditions. The number of density-arc-minutes that density is above a critical free flow density conveys a measure of total congestion. This density data can be made available for a TMC, as well as in simulation. An example is given of the use of the Kruskal-Wallis test statistic in finding significant differences in maximum densities for four routing strategies.
This paper presents an innovative approach to Advanced Traffic Management and Information Systems... more This paper presents an innovative approach to Advanced Traffic Management and Information Systems that integrates real-time supply- side network capacity management with demand-side dynamic route choice. In this approach, local network managers oversee and direct flows toward optimality and drivers autonomously select routes in- vehicle in a viable partnership. Simulation modeling of dynamic peak period demands is used to study trip and network performance under four scenarios. It is shown that a mixed strategy, termed Arc Metering and which incorporates metering of network arcs as a supply- side management strategy, provides significant savings in travel time while enabling the network to accommodate higher volumes of peak- flows.
This paper has been mechanically scanned. Some errors may have been inadvertently introduced. CAL... more This paper has been mechanically scanned. Some errors may have been inadvertently introduced. CALIFORNIA PATH PROGRAM
~s one of ten regmnal umts mandated by Congress and estabhshed m Fall 1988 to support research, e... more ~s one of ten regmnal umts mandated by Congress and estabhshed m Fall 1988 to support research, educataon, and tralmng m surface transportatmn The UC Center serves federal Regmn IX and is supported by matching grants from the U S Department of Transportatmn, the Cahforraa Department of Transportation (Caltrans), and the Umvers~ty Based on the Berkeley Campus, UCTC draws upon exxstang capablhtles and resources of the Instatutes of
It has been contended that in-laboratory experimentation with interactive microcomputer simulatio... more It has been contended that in-laboratory experimentation with interactive microcomputer simulation can substitute for the lack of real-world applications and provide a useful approach to data collection and driver behavior analysis. With the rapid development but limited real-world deployment of Advanced Traveler Information Systems, interactive simulation has quickly grown in popularity among researchers studying dynamic driver behavior. This paper discusses the development and implementation of FASTCARS (Freeway and Arterial Street Traffic Conflict Arousal and Resolution Simulator), an interactive microcomputer-based animated simulator designed for in-laboratory experimentation to assist in the estimation and calibration of predictive models of driver behavior under the influence of real-time information.
Optimally routing vehicles over time and space is a central theme within real-time traffic manage... more Optimally routing vehicles over time and space is a central theme within real-time traffic management. This paper explores the application of a distributed artificial intelligence multiagent system that uses principled negotiation to improve dynamic routing and traffic management within roadway networks. On the demand side vehicles of individual drivers are equipped with intelligent route guidance systems capable of seeking and acquiring knowledge and assisting the traveler in developing trip itineraries. Real-time control over the transportation network is accomplished through an agent-based distributed hierarchy of system operators. Traveler information is gathered and disseminated by information service providers. Through pre-trip and en-route principled negotiation between agents, network performance is enhanced from the point of view of both drivers and system operators. The paper also demonstrates how this view of traffic management complements and builds upon the National ITS...
Transportation Research Record: Journal of the Transportation Research Board, 1998
For a wide range of transportation network path search problems, the A* heuristic significantly r... more For a wide range of transportation network path search problems, the A* heuristic significantly reduces both search effort and running time when compared to basic label-setting algorithms. The motivation for this research was to determine if additional savings could be attained by further experimenting with refinements to the A* approach. We propose a best neighbor heuristic improvement to the A* algorithm that yields additional benefits by significantly reducing the search effort on sparse networks. The level of reduction in running time improves as the average outdegree of the network decreases and the number of paths sought increases.
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