United States Department of Transportation
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Evaluation Of The Advanced Operating System Of The Ann Arbor Transportation Authority: Evaluation Of Automatic Vehicle Location Accuracy
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1999-10-01
[PDF-84.50 KB]
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TRIS Online Accession Number:00801423
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NTL Classification:NTL-PUBLIC TRANSPORTATION-Advanced Public Transit Systems;NTL-PUBLIC TRANSPORTATION-Bus Transportation;NTL-GEOGRAPHIC INFORMATION SYSTEMS-GEOGRAPHIC INFORMATION SYSTEMS;NTL-INTELLIGENT TRANSPORTATION SYSTEMS-INTELLIGENT TRANSPORTATION SYSTEMS;
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Abstract:In 1997, the Ann Arbor (Michigan) Transportation Authority began deploying advanced public transportation systems (APTS) technologies in its fixed route and paratransit operations. The project's concept is the integration of a range of such technologies into a comprehensive system, termed the "Advanced Operating System" (AOS) to "smart buses", "smart travelers," and a "smart operation center" to benefit from timely and coordinated information on critical aspects of transit operation and maintenance. This study assesses the accuracy of the Automatic Vehicle Location (AVL) data provided for the buses of the Ann Arbor Transportation Authority with Global Positioning System (GPS) technology. In a sample of eighty-nine bus trips two kinds of accuracy were gauged: 1. The reported accuracy of bus locations compared to known bus stop locations; and 2. The accuracy of audio announcements relative to their corresponding stops. The median positional error was 85 meters ranging as high as 580 meters and as little as 3.25 meters. The frequency distribution of errors implied that some nonrandom process was leading to the errors observed. To seek to determine the nature of such nonrandom process, error patterns were examined for directional bias, but none was found. In contrast, a spatial analysis of errors showed that errors in central Ann Arbor tended to be smaller, with larger errors in outlying areas. It may be that receipt of the differential GPS correction deteriorates in outlying areas, leading to increased errors. Most stop announcements were within acceptable distance from the bus stops to which they referred, though a small minority (fifteen percent) were triggered as close as 25 meters or as far as 450 meters from the stop. Positional error, rather than any other electronic malfunction, appeared to be behind observed in stop announcements. Figures, table, appendix, 27p. It should be noted that pages 15-19 are blank.
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