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OCR for page 70
70 capacity is normally not considered in this exception at all, a where each of the above terms has a precise technical definition, type of partial service credit is allowed in one specific case-- and is subject to recordation of actual conditions. A Mode Downtime Event is an event in which one or more during a failure of the scheduled single train operation when Operating System-related problems cause an interruption of the the standby train is undergoing maintenance and is unavailable. normal service provided by the desired operating mode. When such an interruption occurs, downtime for the event shall include 188.8.131.52 System Service Availability Method all the time from the beginning of the interruption until all trains stopped on the guideway are restarted and normal operation in The System Service Availability Method has been advo- the scheduled mode is restored (i.e., continuously and normally cated and used by U.S. consulting firm Lea+Elliott since equal train spacing). Downtime events of a duration that are less than one operational headway shall not be counted in the calcula- 1994. As a result, it is in wide usage at airport APMs world- tion of service mode availability, but shall be counted for down- wide. The method is distinguished from the other methods time limits purposes. A train stopping on the guideway or failing by measures that record the performance of subsystems to depart from a station shall be considered a mode downtime that are most likely to affect passengers. Because the other event. Stoppages resulting from causes listed in the following as methods concentrate only on performance as affected by inter exclusions shall not be counted as mode downtime events. Exclusions. The following events are not attributable to the ruptions to system service (i.e., train stoppages), other fail- Operating System itself and are not mode downtime events. ures that affect passenger service without interrupting system Delays due to these exclusions are not to be used in determin- service are not captured. For example, station platform door ing service mode availability, and shall result in the entire period failures that deny passengers access to the vehicles affect affected by them being deleted from consideration in calculating passenger service and may not be reflected in the measures service mode availability (i.e., Scheduled Mode Operating Hours is reduced), but not from data collection and storage. All data of the other methods. This method incorporates measures collection means shall include all periods of time. of service mode availability, fleet availability, station plat- form door availability, and system service availability. The 1. The time period to transition from one scheduled operating additional availability measures related to fleet and station mode to another scheduled operating mode or adjusting sched- platform doors ensure that all failures affecting passengers uled fleet size. Valid transition periods shall not be counted in calculating Am. Time in excess of allowable transition time by (not just those that interrupt service) are reflected in the overall more than one operational headway, as operated during the peak service availability measure. period for the route, shall not be excluded, but the availability The System Service Availability Method also tracks the achieved during that period shall be adjusted by a "K" factor. number of service mode failures, or downtime events, which The time to change into and out of a lesser, nonscheduled, allows measures of service mode reliability and maintainabil- operating mode due to a failure of the scheduled, or higher- order backup, operating mode shall not be excluded, but shall ity to be easily made. These two measures, along with the four be counted as the lower of the operating modes. availability measures described previously, make up the six 2. Passenger-induced interruptions or delays. measures unique to this method. 3.Interruptions caused by intrusions of unauthorized persons or The method allows an equivalent of one headway dura- of animate or inanimate objects into non-public areas of the tion or less for a grace period for both incidents/failures and Operating System. 4. Interruptions caused by non-Operating System induced loss schedule transitions. It also allows for the consideration of of service, e.g., loss of utility service, electrical power provided downtime credit for partial service operations provided during outside the nominal range, vehicle diversion resulting from failures, and it considers capacity as part of its normal measure intended security responses, force majeure, and acts or omis- set rather than during partial service credit only. sions of the Owner or its agents or contractors. The System Service Availability Method, as excerpted in 5. Periods of scheduled operating times when the specified envi- ronmental limits are exceeded. the following, discusses the four measures of availability. 6.Periods when the Fixed Facilities are not available, unless their Measures of service mode reliability and maintainability pre- unavailability is attributable to the Contractor or its vehicles/ viously discussed in this subsection are not presented in the subsystems. excerpt for the sake of brevity [2.2.6]. 7. Operational delays induced by the ATC system to regulate train operations, maintain schedules and for anti-bunching; where System Service Availability Method Described such delays do not exceed the operational headway for the route. Service Mode Availability K-Factor. Used to calculate partial Operating System mode For each time period and service mode of operation, Service availability during failure mode operations. When the Operating Mode Availability is measured as: System is not in any failure mode, K factor shall be equal to one. If a downtime event occurs and service is not restored within the time specified to that scheduled for the Operating System, but Scheduled Mode Operating Hours rather a lesser service mode is operated for failure management, - Mode Downtime Hours A (m) = then the entire time period for operating in any failure mode Scheduled Mode Operating Hours shall be counted as partial mode downtime. To determine A(m),