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22 tracted service availability on the basis of service unavailabil- ity performance. Measures that are set forth include headway ity, and in so doing, eliminates from the calculation any need adherence, service regularity, headway ratio, headway regu- to consider grace periods or the downtime exclusions common larity index, and headway deviation. to the other methods. (The other methods are similar in that The ultimate conclusion is that network configuration they exclude the consideration of downtime caused by exter- affects the reliability and availability of airport APMs, albeit nal sources, such as passenger-induced delays, interruptions in a limited way due to the limited variety of airport APM caused by intrusions of unauthorized persons or objects, and networks. Other system parameters such as consist size and other external sources beyond the control of the system or the number of in-service trains also affect reliability and operating entity.) availability. Working from the perspective of service unavailability, the goal of this method is to take into account the transporta- tion capacity of the system during periods of degraded mode and Measuring Service Availability operations. Providing the ability to earn this partial service for Complex Transportation Networks credit, and tying the contracted service availability to pay- The second paper, "Defining and Measuring Service Avail- ment, is an incentive to the operator to provide the best ability for Complex Transportation Networks," was presented possible transportation capacity during failures. Although the in 1996 at the International Conference on Personal Rapid path to calculating the contracted service availability number Transit (PRT) and Other Emerging Transportation Systems is different, the partial service credit incentive concept is in Minneapolis. It was written by Charles P. Elms, now retired very similar to the approach used for the Chicago O'Hare from Lea+Elliott. APM discussed previously. One significant difference is that The paper first defines measures of service availability in whereas the Chicago APM must deal with a specific approach current use and analyzes exact and approximation methods due to its variable-length trains, the CDG APM system does for data collection and computation. It then postulates and not (it has fixed-length trains). Both of these APM systems, explores classical and new definitions of service availability Roissy Charles-de-Gaulle and Chicago O'Hare, are supplied applicable for complex networks such as PRT. Insight is pro- by the same APM system supplier, which may explain some vided for choosing a suitable definition based on the type of of the similarities in the methods. transportation network. The methodology in the paper is based on the classi- 4.1.2 Theoretical Methods cal approach of service mode availability [MTBF/(MTBF + MTTR)], and adjusts for fleet availability and station platform The literature review and analysis have also revealed that APM performance measurement has been studied and re- door availability. Ultimately, the methodology outlined in ported on theoretically. Three papers in particular have been the paper aligns with the System Service Availability Method presented in this area. discussed previously. APM Performance Measurement: Reliability, Availability Network Configuration and Maintainability of APM Systems and Service Availability The third paper, "RAM: Reliability, Availability and Main- The first paper, "Airport APM Performance Measurement: tainability of Automated People Movers," was presented in Network Configuration and Service Availability," was pre- 1989 by John K. Howell at the Second International Conference sented in 2007 at the 11th International ASCE APM Confer- on APMs in Miami. ence in Vienna. It was written by Wayne D. Cottrell, Associate This paper discusses in detail reliability theory in particu- Professor at California State Polytechnic University, and Yuko lar, as well as the factors that influence reliability (MTBF), J. Nakanishi, President of Nakanishi Research and Consult- maintainability (MTTR), and availability in an APM system. ing, LLC. It also describes approaches to specifying contract service This paper examines service availability and reliability and requirements based on classical definitions of MTBF, MTTR, how they are affected by airport automated people mover and availability. The paper ends with a discussion of RAM (AAPM) network configurations and other system parameters. monitoring and accountability. The paper affirms the importance of availability and reliability The methodology in the paper is generally based on the measurements in the APM industry. classical approach of availability [MTBF/(MTBF + MTTR)] The paper suggests that detailed measures of headway regu- and aligns with the Contract Service Availability Method dis- larity would be useful in an empirical study of AAPM reliabil- cussed previously.