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9 enjoys a comprehensive archive of high-quality location data, Service making it a leader in archived AVL-APC data analysis. Plan NJ Transit took a still more radical step in designing, in con- Analyze junction with an AVL vendor, an AVL-APC system that, for the Performance and Demand time being at least, does not include real-time radio communi- Operational cation. Although they envision integrating radio in the future, control & Transit Passenger Operation the current configuration is strictly for off-line analysis. info Archive In the Netherlands, AVL systems with on-board data Data recording were installed in some cities in the early 1990s. Real However, the lack of analysis tools and poor quality of base Off-line time Automated maps led to their data being largely unused until about 1996, loop loop Data when the Delft University of Technology teamed up with the Gathering municipality of Eindhoven and its transit operator, Hermes, to improve their data quality and develop and apply analysis Figure 1. Service quality improvement cycles. tools. Those tools, originally developed around 1980 for use with manually collected data, were coded into the software (e.g., 0 to 3 min late). For real-time control, or even passenger package TriTAPT (Trip Time Analysis in Public Transport), information, exception data like this may be adequate; how- which has also been applied at transit agencies of the Hague, ever, a data stream containing only exception data is entirely Rotterdam, and Utrecht. unsuitable for analyzing running time. Another difference is A significant recent development for archived AVL-APC that real-time data is more tolerant of errors. If faults in either data is the growing demand for stop announcement systems, the location system or the base map make a bus's apparent track which require considerable on-board computing power to momentarily jump a few miles off route, service controllers match stops in real time. The creators of those systems found it learn quickly how to ignore such anomalies; however, in a data easy to simply add data recording, creating a new function for archive, such errors may go undetected and distort running their product and thus creating a new source of archived AVL time or schedule deviation analyses. data--one that promises to be very accurate by virtue of being APC systems, unlike AVL, have always been oriented designed for a rather demanding application. In the system toward off-line analysis. Historically, APC systems were inde- installed in the Chicago Transit Authority (CTA), APCs have pendent of (real-time) AVL systems. Their adoption has been also been integrated on a sample of the fleet. far more limited than AVL systems. The weaker market for The movement to integrate systems and on-board devices APCs has resulted in several vendors having gone out of busi- is serving to blur the distinction between what first appeared ness and has limited the amount of vendor-developed soft- as stand-alone systems. In recent years, for example, some ware for data analysis. (That trend, fortunately, is being cities, including Minneapolis, have integrated APCs into reversed as technology advances.) Transit agencies have been real-time AVL systems, with stop data transmitted over the air largely left on their own to develop their APC systems; pio- to a central computer for archiving. APC and event record- neering successes include transit systems in Seattle, Ottawa, ing has been added to stop announcement systems, and stop Winnipeg, and Toronto. announcements have been added to real-time AVL systems. A radical shift in AVL system development in favor of However, regardless of what functions a data collection system archived data collection occurred in the mid-1990s, when Tri- may have, there are common needs for archived data analysis. Met, together with an AVL vendor, designed a hybrid AVL-APC Therefore, this report will sometimes use the term AVL in a system featuring on-board event recording and radio-based generic sense, meaning any automatic data collection system communication. Records for every stop and other events are that includes location data. created in the on-board computer, while messages useful for real-time monitoring (e.g., bus is late or off-route) are radioed 1.2 Research Objective in. Another innovation was that APCs, installed on a sample of the fleet, do not have their own location system; they simply Technological advances erase all question of the feasibility count passengers and rely on the AVL system to provide the of collecting and archiving high-quality location data. Two location stamp. This design lowered the marginal cost of instru- primary issues remain: menting buses with APCs to the point that all new buses at Tri- Met now have APCs. With 65% of the fleet equipped, Tri-Met How should automatic data collection systems and their stands out as the only agency with more than 20% of its fleet associated databases and software be designed so that they APC-equipped. After a few years' break-in period, Tri-Met capture and facilitate the analysis of AVL-APC data?