Plan for cellular communications to evolve and transition to new communication technologies every few years.
A synthesis of transit agency experience with bus AVL systems
In late 2000, TTA implemented an AVL system. The initial deployment included 68 buses and used onboard mobile data terminals (MDT) with an integrated GPS receiver and Cellular Digital Packet Data (CDPD) cellular mobile data communications capability. By late 2005, CDPD technology was phased out by the cellular service provider in favor of Code Division Multiple Access (CDMA) technology. The AVL system required significant upgrades, and until the AVL system could be retrofitted with new technology, mobile communications were unavailable. By April 2007, an operational pilot version of the updated MDT with CDMA technology was received and integrated into the central AVL system.
The following lessons learned were identified as the integration work and system upgrade were nearing completion in 2007.
- Anticipate and plan for cellular technology to evolve and transition to new communication technologies. Prepare to retrain staff including operators, dispatchers, supervisors, maintenance technicians, information technology staff, customer service, and marketing personnel.
- Communicate proactively with cellular service providers and technology vendors. Consultants are an additional resource applied selectively by agencies, for areas where staff have less experience with regard to technology upgrades.
- Budget for periodic minor upgrades required to maintain compatibility with cellular data service at it evolves and improves. Carefully select the systems integrator, apply strong project management for implementation, and understand that substantial ongoing effort will be need to manage AVL system operations.
Although cellular data services offer reduced costs relative to the implementation of an agency-operated mobile data system, agencies should expect cellular data systems to evolve at least every few years. Recently, "mesh" networks have been developed to support high-data rate mobile communications. Mesh networks combine multiple technologies to reduce the number of access points on a network backhaul that connect directly to a central system (i.e., dispatch). With fewer access points, communication costs are reduced. Mesh networks limit the number of access points by reconfiguring some access points to act as repeaters and funnel information wirelessly to individual nodes on the network backhaul. Other strategies use onboard systems that act as repeaters to share information between buses prior to accessing the backhaul.
Transit agencies that offer hotspots, onboard Internet access, or require bulk data transfers during maintenance activities can benefit from technologies that improve high-data rate mobile communications. A state-of-the-art communications system is key to improving the efficiency, mobility, and productivity of transit operations.
Author: Doug J. Parker
Published By: Federal Transit Administration
Source Date: 2008URL: http://onlinepubs.trb.org/onlinepubs/tcrp/tcrp_syn_73.pdf
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Intelligent Transportation Systems > Transit Management > Operations & Fleet Management > Automatic Vehicle Location / Computer-Aided Dispatch
Intelligent Transportation Systems > Transit Management > Operations & Fleet Management > Planning
Intelligent Transportation Systems > Transit Management > Operations & Fleet Management > Maintenance
Intelligent Transportation Systems > Driver Assistance > Driver Communication > With Carrier/Dispatch
automated vehicle location, computer aided dispatch, automatic vehicle locator, AVL, CAD, AVL/CAD