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72 in 1996 at the International Conference on Personal Rapid 2.3.1 Historical Development Transit (PRT) and Other Emerging Transportation Systems in Minneapolis [2.2.7]. It was written by Charles P. Elms, a There is a large literature base that exists today about former Principal of U.S. consulting firm Lea+Elliott, Inc. performance measures in the transit industry. However, two The paper first defines measures of service availability in or three decades ago, the landscape on transit performance current use and analyzes exact and approximation methods measures was fairly similar to that of airport APM systems for data collection and computation. It then postulates and today. That is, no systematic approach existed. explores classical and new definitions of service availability Some early documents on transit performance evaluations applicable for complex networks such as PRT. Insight is pro- can be traced back to the early 1980s [2.3.1, 2.3.2, 2.3.6, and vided for choosing a suitable definition based on the type of 2.3.22]. Based on the fact that most obstacles to the compara- transportation network. tive evaluation of transit performance lie chiefly in the non The methodology in the paper is based on the classical conformity and inaccuracy of the data and the inadequate approach of service mode availability [MTBF/(MTBF + coverage of the local operating characteristics, studies around MTTR)], and adjusts for fleet availability and station plat- this period tended to address the need for data collection form door availability. Ultimately, the methodology outlined in and systematic analysis of the data collected. After May 1981, the paper aligns with the System Service Availability Method however, this first obstacle was overcome with the publication discussed previously. of the annual reports required by Section 15 of the Urban Mass Transportation Act of 1964 [2.3.1]. However, the data analysis techniques were limited to rudimentary statistical 2.2.2.3RAM: Reliability, Availability correlation and regression analysis [2.3.2], and performance and Maintainability of APM Systems measures were still in the stages of infancy [2.3.6]. This The third paper, "RAM: Reliability, Availability and Main- Section 15 reporting by U.S. transit agencies continues but tainability of Automated People Movers," was presented in is known today as the National Transit Database [2.3.12]. 1989 by John K. Howell of U.S. consulting firm JKH Mobility The NTD program is discussed in more detail later in this at the Second International Conference on APMs in Miami section. [2.2.11]. Another trend in the early development of transit perfor- The paper discusses in detail reliability theory in particu- mance measures was the mode-specific approach, which is lar, as well as the factors that influence reliability (MTBF), still practiced today and may have potential to be applied to maintainability (MTTR), and availability in an APM system. airport APM systems. Topp [2.3.18] conducted an extensive It also describes approaches to specifying contract service study of Toronto Light Rail services to identify potential prob- requirements based on classical definitions of MTBF, MTTR, lems, practical performance measures, and policies linked and availability. The paper ends with a discussion of RAM with performance evaluations. Rouphail [2.3.15] examined monitoring and accountability. performance evaluation of bus priority measured in the The methodology in the paper is generally based on the Chicago Loop. And Lauritzen [2.3.8] examined the first year classical approach of availability [MTBF/(MTBF + MTTR)] operation of the Chicago Transit Authority's special services, and aligns with the Contract Service Availability Method dis- using performance measures tailored to those services. cussed previously. An early framework for transit performance concepts was presented by Fielding [2.3.3], where cost efficiency, service effectiveness, and cost effectiveness were the terms used 2.3Public Transit Performance to describe the three dimensions of transit performance. Measurement Other studies [2.3.4 and 3.3.5] applied this framework for This section is a summary of the key findings of perfor- performance evaluation. mance measurement used in the public transit industry. Lew, Li, and Wachs [2.3.9] carried the framework of transit It contains subsections with discussions in three areas: the performance measures one step further by defining several historical development of public transit measures, provid- categories of common indicators. They identified three critical ing a brief overview of the history and current practices of limitations to commonly used performance indicators and perfor mance measurement in the public transit industry; proposed a new set of intermodal performance indicators. The concentrated efforts in the area of public transit performance new proposed indicators overcame the limitations of single- measurement, focusing on two efforts of performance mea- mode indicators by incorporating mechanisms for comparison surement in the transit industry; and international practices, of one mode to another, for rating the performance of systems containing examples of measuring transit performance in the that include multiple modes, and by incorporating both capital international arena. and operating costs.