Application: Agent-Based Real-Time Traffic Detection and Management System
System Organization
Agent-based real-time traffic detection and management system (ABRTTDMS) is an IEEE FIPA compliant multi-agent application aimed at providing real-time traffic conditions, predicting potential incidents, and alarming the predefined events to the traffic management center (TMC). The real-time traffic information detected by the system can also be used as the source of intelligent traveler information systems, which provide information, such as travel time, to travelers. The system architecture has multiple levels as shown in the Figure below. The lowest level is composed of various detectors such as loop detectors, laser detectors, and video cameras. Laser detector agent (LRDA), loop detector agent (LPDA), and video camera detector agent (VCDA) are used to process the output of the corresponding detectors and provide the desired intelligence. A traffic detection execution system (TDES) agent coordinates all of the LRDAs, LPDAs, and VCDAs in a sub-network and communicates with other TDES agents and an upper-level TMC agent. TMC agent delegates tasks to the lower-level agents and analyzes the information from these agents. It also dispatches mobile agents to different agencies to perform certain tasks. Because the system architecture is open, new detection systems can be easily integrated into the system by wrapping them into agent-based sub-systems.

The Organization of ABRTTDMS

Laser-Based Vehicle Detection System

Laser-Based Vehicle Detection System
Either laser detectors or loop detectors can detect the real-time traffic parameters. In current ABRTTDMS implementation, real-time traffic parameters are detected by the laser-based vehicle detection system shown below. The detection system was developed in the Integration Engineering Lab at the University of California, Davis sponsored by Caltrans. The laser-based detectors are designed to detect the delineations of passed vehicles, such as length, width, and velocities. The real-time detection data are sent to LRDAs continuously. Vehicle re-identification is to be realized and the link travel time between two LRDAs is to be estimated based on the information of two consecutive LRDAs, typically called the upstream and downstream LRDA. LRDAs can also be used to accomplish traffic density estimation and incident detection on the segment of a freeway. The video cameras in the system are used to verify the incidents. The VCDA controls the operation of different cameras, processes the video stream, and estimates the required traffic parameters.
The Functionalities of Stationary Agents in ABRTTDMS
  • Laser detector agent (LRDA)
    • Process real-time data from laser detectors.
    • Realize vehicle re-identification, estimate travel time and density on a freeway segment; detect incidents.
    • Improve detection algorithms and select proper algorithms dynamically.
    • Track real-time traffic conditions and alarm the TMC when predefined events occur.

  • Video Camera Detector Agent (VCDA): The function of VCDAs is to control different cameras to verify incidents. As previously described, LRDAs or LPDAs can detect incidents based on link travel time checking. However, LRDAs or LPDAs cannot provide exact incident location and other detailed incident information. VCDAs in the system are designed to provide this information when incidents occur. For example, when the downstream LRDA finds that the link travel time exceeds the reasonable time window, it reports this event to the TDES agent in the sub-network. The TDES agent requests the VCDAs in the area to check the traffic condition in a certain area. The VCDAs select proper cameras to take pictures and analyzes input video streams to obtain the request incident information.

    The Modular Structure of an LRDA

    The Functionalities of TDES Agents

  • Traffic Detection Execution System (TDES) Agent: A TDES agent is a coordinator of lower level agents in a freeway sub-network. All of the lower level agents register themselves and their services with a TDES agent. A TDES agent has the knowledge of geographical distribution of lower level agents and their capabilities. The tasks of TDES agents are shown in the above Figure.

  • Traffic Management Center (TMC) Agent: TMC agent is located in traffic management center. TMC agent delegates tasks to the lower level agents and analyzes the information from these agents. It can also connect to any agent in the region and dispatches mobile agents to different agencies through a user graphical interface. The specific tasks of TMC agent is as follows:
    • Interface with the personnel at the TMC to accept human commands.
    • Generate tasks dynamically and delegate these tasks to lower level agents.
    • Analyze the information from lower level agents and generate reports or control proposals to the personnel at the TMC.
    • Create mobile agents and dispatch them to different agencies to perform certain tasks.
Mobile Agents in ABRTTDMS
ABRTTDMS has two types of agents, stationary agents and mobile agents. LRDAs, LPDAs, VCDAs, TDES agents, and TMC agent are stationary agents. Mobile agents are those, which can migrate among different agencies. Mobile agents are used for dynamic extension of system functionality. For example, the operators at the TMC might want to know the number of vehicles passed under certain detection stations from 12:00pm to 1:00pm on certain day. Because this functionality was not implemented at the design stage, the existing code cannot provide required information. To obtain additional information, raw data have to be sent to the TMC. The raw data generated by laser detectors in our system are huge. Instead of moving raw data, we move computation to the data source. Mobile agents equipped with appropriate computational capabilities can migrate through different agencies in the detection network. At each agency, to which mobile agents migrate, they access raw data, process raw data locally, and send back results to their dispatcher -- TMC agent. Using mobile agents can avoid transferring a huge volume of raw data to the TMC, reduce the network transmission load, and overcome the network latency.
Graphical User Interface of TMC Agent
The graphical user interface (GUI) of TMC agent is shown below. GUI displays the locations of all the stationary agents in the area. It can also graphically show the distribution of stationary agents. Through this GUI, users are able to connect or disconnect to any stationary agent in the system and acquire required information. Users can also create mobile agents and dispatch them to different agencies. The results obtained by these mobile agents are sent back and displayed in the "Information from Mobile Agents" window in the GUI. Mobile agents are created and dispatched to different agencies through following procedures. Activating menu item "MobileAgents" in the menu bar and selecting "Create" item in the pull-down menu bring up a dialog box as shown below. After filling in each entry in the dialog, the user can create a new mobile agent by clicking the "Create" button at the bottom of the dialog box. To dispatch a mobile agent, the user can activate menu item "MobileAgents" and select "Dispatch" item in the pull-down menu. In the pop-up dialog box, the user specifies the name of mobile agent that is to be dispatched and clicks the "Dispatch" button to dispatch the mobile agent.

The Graphical User Interface of TMC Agent

The Dialog Box to Create a Mobile Agent

System Control Architecture
ABRTTDMS employs dynmic hybrid control architecture. System's hierarchy has three levels as showm in the figure below. Agents at the same level can interact with each other. The highest-level agent is the TMC agent, TDES agents sit at the middle level, and LRDAs, LPDAs, and VCDAs are at the lowest level. Under certain scenarios, a number of heterogeneous lowest level agents are dynamically grouped and interact with each other to accomplish a task. For example, when the task is to find travel time, the involved lowest agents are only LRDAs. Different LRDAs are dynamically grouped to perform the tasks related to different areas. When the task is incident verification, VCDAs will also be grouped into the cluster. A TDES agent accomplishes the coordination of these agents in a sub-network.

The Control Architecture of ABRTTDMS

The Rconfigurable Feature of ABRTTDMS