Computer Aided Service Restoration (CASR) In CAD/AVL Systems

Transcription

1 Computer Aided Service Restoration (CASR) In CAD/AVL Systems Joachim Pfeiffer INIT Innovations in Transportation, Inc. Chesapeake, VA ABSTRACT A major purpose of the implementation of Computer Aided Dispatch / Automatic Vehicle Location (CAD/AVL) systems is to create a real-time representation of fleet operations to dispatchers. This representation is used to inform dispatchers about location of vehicles and their schedule adherence. During real-time operations, not everything goes according to schedule, and dispatchers are forced to intervene in regular operation and activate procedures like short turn or vehicle exchange in order to restore the service. Therefore, it is necessary to consider these measures in a CAD/AVL system and implement features to support the dispatchers in their daily work. Advanced features connection protection and distance control take advantage of the real-time information provided by CAD/AVL systems, and automatically control real-time operations. This paper describes Computer Aided Service Restoration (CASR) as a set of features based on CAD/AVL systems. CAD / AVL FEATURES AND COMPONENTS Computer Aided Service Restoration (CASR) is based on Computer Aided Dispatch / Automatic Vehicle Location (CAD/AVL) systems. CAD/AVL systems typically consist of a transit vehicle fleet where each vehicle is equipped with a location device such as a GPS receiver, with a data radio capable mobile radio, a data radio modem, and a Vehicle Logic Unit (VLU). The VLU controls these components, and provides the functions necessary for automatic vehicle location. Additional equipment can be connected to the VLU. Typically, a Mobile Data Terminal (MDT) for vehicle operator interaction is installed, in order to support computer aided dispatch based on operator inputs at the MDT. The MDT has a keyboard and a display. Using the keyboard, vehicle operators input route/block-, driver id numbers and other information. Via VLU, data radio modem and data radio, inputs are transferred to the CAD/AVL control center. The MDT s display shows information obtained from the CAD/AVL control center like current time, schedule adherence and other information. On top of these basic CAD/AVL functions, equipment like voice radio and public announcement systems, automatic next stop annunciators, headsigns, on-board next stop displays, automatic passenger counters, traffic signal priority systems, fareboxes, engine health check sensors, odometer, door open/close contacts and wireless LAN adapters are often connected to and integrated with the VLU, usually as purpose and funding of the CAD/AVL system allow and/or require. Figure 1 shows an example vehicle configuration with VLU, MDT and peripherals. In the CAD/AVL control center, a CAD/AVL server maintains operational data gathered over data radio from the transit vehicle fleet. Supplied with the schedule of the current operational day, the CAD/AVL server compares the current operations with the schedule. The resulting schedule adherence values are transferred to the transit vehicle fleet, and dispatch workstations are supplied and updated with this data. Based on the schedule adherence values dispatchers are provided with information about the transit vehicle fleet s operation. Figure 2 shows an example of a MDT display with schedule adherence value and other information. For passenger information wayside, variable Message Signs (VMS) at bus stop positions and displays in transfer centers are supplied with estimates of the departure times of the next bus by the CAD/AVL server. There are three types of operations which are supported by CAD/AVL systems: Bus fixed-route Bus on-demand (Paratransit) Rail fixed-route Transit Agencies (TA) with several types of operations require integration of the different types, e.g. integration of bus fixed-route and Paratransit services, if single blocks contain trips of both services. 1

2 Figure 1. Typical vehicle configuration. 2

3 Figure 2. Example of a mobile data terminal display. 3

4 CASR STANDARD AUTOMATED DISPATCH FEATURES CAD/AVL systems operated at the level described above, must provide features which map regular dispatch activities like short turns on-line, i.e. in real-time to automated dispatch features. The fully integrated implementation, affecting CAD/AVL server, data radio and the vehicles VLU/MDT-sets, of regular dispatch activities is inevitable, due to the following reasons: Reduction of voice radio communications and vehicle operator interaction: For example, a short turn does not have to be announced to the vehicle over voice radio, and is automatically considered in automatic next stop announcements and headsigns settings. Accuracy of estimates of next stop displays at bus stop positions. For example, a cancelled trip must be taken out from consideration on next stop displays. Statistical evaluation (post-processing): For example, after cancellation of a trip, a vehicle operator must not be charged with an early pull-in. Enhancement of vehicle and control center equipment benefits: Vehicle equipment and radio system are usually the most costly part of a CAD/ AVL system. The installed hardware must be utilized as far as possible. The following CASR dispatch features must be provided for a CAD/AVL system (in brackets: CAD/AVL-type of operation): Short turn (bus fixed-route): A bus turns before terminus. Cut/cancel trip (bus fixed-route, Paratransit, rail fixed-route): A trip is removed from a block. Copy trip (bus fixed-route, Paratransit, rail fixedroute): A trip is copied from a block into another, the same, or a new block. Create trip (Paratransit): A trip is created when a registered passenger requests a trip for the current operational day. Assign vehicle to route/block number (bus fixedroute, Paratransit, rail fixed-route): Override a vehicle operator s route/block input. Detours (bus fixed-route, Paratransit): Consideration of road blocks. Platform change (rail fixed-route): A train uses another platform. Driver assignment (bus fixed-route, Paratransit, rail fixed-route, if drivers and duties are managed by the CAD/AVL system): Override a vehicle operator s driver id input. All CASR dispatch features are initiated by dispatchers on their workstations. Before a CASR dispatch feature is executed, the CAD/AVL server must simulate the requested action, and inform the dispatcher about the result. Simulation before execution is required in order to avoid unintentional attempts like cancellation of the last trip of a route, or short turn before a predefined passenger transfer. CASR ADVANCED AUTOMATED DISPATCH FEATURES IT systems generally have many benefits, which go beyond the automation of existing business activities. Based on the computers potentials, additional function are supplied. In the context of CAD/AVL systems, the standard automated dispatch features represent automation of a certain part of a TA s every-day business. They compare to the ability of a word processor-and-printer-set to print out characters which have been typed on a keyboard like a typewrite does. Word processors provide much more sophisticated features, which have been unknown in the typewrite-age, e.g. copy-and-paste of text, and integration of images. In CAD/AVL systems, these more sophisticated features are advanced automated dispatch features, which can not be accomplished manually due to excessive communications and manual interaction requirements. These advanced features are (in brackets: CAD/AVL type of operation): Compound standard automated dispatch features (bus fixed-route, Paratransit, rail fixed-route): Standard automated dispatch features are used as building blocks to construct more complex automated dispatch features, e.g. vehicle exchange based on two consecutive executions of route/block assignment, or copies of block section (several subsequent trips of a block) by repeated application of copy trip. Trip clipboard (bus fixed-route, Paratransit, rail fixedroute): Several trips which have been cut or copied from a block are stored in a clipboard for later paste operations. Automatic connection protection (bus fixed-route, Paratransit, rail fixed-route): There are two types of 4

5 connections: One-way connections and join connections. At a one-way connection, a block feeds another block with passengers at a stop. Several blocks join and exchange passengers at join connections. In both cases, more than one stop might be involved and must be considered, if stops are within walking distance. The connections are pre-defined in the schedule database, and loaded to the CAD/AVL server. The CAD/AVL server monitors the participating blocks, and informs dispatch, if a connection is endangered. The CAD/ AVL system notifies vehicle operators on the MDT display to hold at a bus stop position, until the last participating block has arrived (plus time for passenger transfer). Connections can be released by dispatch, if blocks follow up on a participating route. Vehicle distance control (bus fixed-route, rail fixedroute): On routes with high frequency, or sections where several routes operate in parallel, passenger value regular intervals over block punctuality. Vehicle distance control calculates the schedule adherence of blocks according to distance to the preceding vehicle, rather than in relation to the schedule. This helps to avoid vehicle bunching. Shift blocks on a route (bus fixed-route, rail fixedroute): If all vehicles on a route are running late, but in relatively regular intervals, the block numbers of the routes are shifted back one vehicle, and a new trip is created to provide service on the last block. Passenger do not mind the particular block they are riding on, so this action can be used to reduce delays on a route without affecting passenger service. ACKNOWLEDGMENTS My thanks go to Achim Becker of INIT GmbH, who has been the first to explore, analyze and implement full integrated standard and advanced automated dispatch features for CAD/AVL systems. 5