| The study focuses on measuring and interpreting the theoretical performance capabilities of transit modes. Line capacity and other performance and efficiency measures related to line capacity are given particular emphasis. The analysis is done in the context of a hypothetical transit system with assumed operating and design characteristics (station spacing, line length, stop schedule, etc.). By this approach, certain limits to transit system performance, cost factors, and service quality variances are observed.;In the process of this analysis, expressions for vehicle, way, and station capacity are derived and variables affecting these measures and the performance and efficiency measures defined are studied. Additionally, new methods for measuring line capacity under varying stopping policies are outlined.;It is concluded that the maximizing of line capacity is coincident with the maximizing of work output (space-kilometers per hour); however, these objectives are attained at sacrifice of other system efficiencies and at higher costs of operation, the latter being measured by a surrogate, fleet size. The maximizing of productive capacity, on the other hand, is generally achieved at much higher optimal speeds than maximum capacity and with superior operational efficiencies and costs than are possible under the capacity objective. The relatively small diminution of line capacity attendant with the productive capacity objective (as compared with the line capacity objective) is generally outweighed by the service quality benefits, the cost reductions, and the fleet efficiency gains accrued.;It is also observed that vehicle dynamic characteristics and transit line characteristics (such as station spacing) impose limits on station capacity, productive capacity, and system efficiency which are not perceived when analysis of line capacity is studied isolated from these factors.;The analysis demonstrates that the maximizing of line capacity has certain limitations as an objective function and as an operational performance measure, both from the perspective of the system operator as well as from that of the system user. A new performance measure concept, productive capacity, is introduced and is tested as an alternative objective function. Productive capacity is defined as the product of line capacity and operating speed. A fleet efficiency measure based on productive capacity is also defined and studied. |
