AVL Systems for Bus Transit: Update (2008) / Chapter Skim
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Pages 91-100
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91 GENERAL ROLE WITHIN AGENCIES The core role of a bus automatic vehicle location (AVL) system, whether for fixed-route or paratransit (demand responsive)
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– Monitor the mechanical status of key components (i.e., from mechanical sensors or electronic control units for components such as engine, transmission, and air conditioning) , recording the data and/or transmitting to dispatch.
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93 – One or more radios to provide wide-area voice and data communications; and – WLAN card to provide bulk data communications at the garage. • Central Systems: – Servers, workstations, and network; – Mobile workstations for selected non-revenue vehicles; – Mobile communications gateways; – WLAN access points network at garages; – Dispatcher software with map and tabular displays showing real-time fleet locations, schedule adherence, and other fleet status information; – APC management software, referring to the software used to manage the processing of APC data received from fleet vehicles; – Software to record and set the text for onboard announcements (some systems use text-to-speech software instead of recording for the audio announcements)
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in this sense covers all system communications beyond the wired Local Area Network (LAN) on agency premises and will be discussed in the following categories: • Onboard • Wide area • Garage bulk data transfer.
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95 • Operating in a relatively extensive or rural service area where setting up voice radio communications infrastructure would be relatively expensive, • Expanding into a new service area, and • Initiating a new or small transit service. Radio Data A bus AVL system requires mobile data communications between the central system and operating fleet vehicles, and often also for communications between the central system and the DMS at selected stops.
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rate supported by cellular data for effective operation (and to avoid overwhelming the data capacity available with radio data channels)
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97 – Many bus AVL systems integrators offer proven offthe-shelf support for the integration of IEEE 802.11b access cards with their VLUs, but in many cases integrators have not yet upgraded their standard solution to support IEEE 802.11g. – Meanwhile, IEEE 802.11n, although still at the prestandard stage, appears to be emerging as the next IEEE 802.11x WLAN technology that will be deployed on a widespread commercial basis.
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to press a button on the headsign controller at the end of each trip of the run, so that the destination is updated. Systems can interface modern headsigns with the VLU by means of the SAE J1708 link.
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99 run schedule manifests, enter trip completion data, and create invoices and reports. Integrating mobile data communications and MDTs with this software creates opportunities to further enhance operations.
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private-sector interests are emerging to use information that transit agencies release even more broadly available to the public. EMERGING TRENDS This section has highlighted several emerging trends whose importance is expected to continue to increase: • Agency-wide data warehousing is expected to become more prevalent and used with increasing effectiveness.
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