November 2000
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November 2000 |
Specification
Change to Create Havoc for Millennium Transit Engineers
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The
Millennium Transit system, slated to serve visitors to the Millennium
Dome in Greenwich, England, has encountered difficulties in implementing the
electronic guidance portions of the system, as reported previously in IVsource.
More details have emerged, which do much to explain why prime contractor Alstom
has asked for a year's extension, or possibly release from the job entirely:
simply put, one change in the specification forced a very different and more
complex system design.
Naturally, Transport for London (formerly called London Transport) wanted to ensure that their system operates safely. Because there was no precedent for this level of automation in buses (automatic lateral control), they turned to the rail safety inspector's office, who assumed authority for safety assurance. The prevailing regulations were applied, which require that the system operate with a driver response time of 2.5 seconds, up significantly from the original spec of 0.6 seconds that Alstom signed up to. This longer driver response time reflects the nature of rail operations, which do not require that the driver exercise as much vigilance as is needed for operating a road vehicle. This seemingly simple change has vastly impacted requirements for system intelligence -- situations which would not be critical for the shorter response time become major challenges for the system. An example would be a bicyclist who may have fallen on the trackway -- with a 0.6 second driver response time, the driver would recognize the situation and stop the bus. But with a 2.5 second response time, it is quite possible that the speed of the bus calls for the system to recognize the situation and stop the bus, therefore creating challenging requirements for obstacle detection and avoidance. There are many changes impinging on the Millennium Line, not the least of which may be the results of political wrangling over the future of the Dome itself. Look for more details to emerge in coming months. [Top]
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Copyright 2000: IVsource.net and Richard Bishop Consulting (RBC). All Rights Reserved. |
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November 2000 |