Principles of System Design

  • In order to be usable, any transportation system must reach a critical mass of development. This critical mass must be significant enough to facilitate system usage by the majority of potential riders while not overextending the system such that the marginal costs of serving the last frontier of potential demand are disproportionately high compared to the costs of serving the majority of riders.
  • For any part of a system to be usable, all parts of that system must be usable. For commuter and other long-distance services, this means that both collector and feeder services at both ends of the long-distance link must be available and sufficient — including the requirement that both service frequencies and coverage be adequate to minimize transfer time and walking distance.
  • Walking or wheeling are essential components of all transportation system usage. As a consequence, not only must stop spacing be optimized and barriers to reaching and using them removed (including stop security), but the pedestrian environment within walking or wheeling distance to all usable stops must also be secure.
  • Passenger rail service usage cannot be maximized without the proper integrated design of other parts of the overall transportation system — including the design of all bus and ancillary modes to provide extensive feeder-to-rail service.
  • Transportation services work best when designed in a hierarchy, and when all members of that hierarchy are simple in design, comprehensible as separate elements, and comprehensible insofar as they fit together. Except in low-density areas, this approach limits the use of do-all services such as regional lines which weave through suburban areas to provide local service at the expense of undermining the travel time benefits of regional services.
  • In the creation of new route designs, every change is an opportunity for performance improvement. Supported with adequate marketing and user information, changes in system designs and design elements help realize these opportunities — even though changes should not be so frequent as to undermine usage stemming from system familiarity and use habits.
  • Services have limited value apart from extensive information available about their usage. In the design of informational materials, emphasis should be placed on user-centric, non-lingual maps and schedules which depict the system from the user’s rather than the system’s vantage point. And materials should be comprehensible to those who do not or cannot read, much less read English or another native language.
  • System characteristics should be accessible to both analog and digital users. The sophistication of transportation technologies should not deter ridership because the mechanics of access are not available, familiar or comprehensible to a segment of the system’s users. Particularly given the high usage of most public transportation systems by elderly individuals (e.g., 60 percent of all motorcoach riders), focusing access to travel information on digital formats is a critical error — an error increasingly being made by transit and paratransit agencies, in particular — whereas, in contrast, taxi and motorcoach services tend to be more “user friendly” to this subpopulation of their ridership, largely by doing things like “getting the phone” without a menu — i.e., the “old fashioned way.”
  • In the provision of demand-responsive and other non-traditional services, it generally costs less to provide high quality and effective service than to provide poorly-designed, unreliable service of marginal quality.
  • Special characteristics integrated into a transportation mode to benefit a special user group often — if not in most cases — provide benefits to the ridership at large. In many cases (e.g., security cameras to monitor student ridership behavior), these characteristics or devices provide equal or greater benefits to other user groups (e.g., elderly and disabled riders).
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