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Network Design

Explore the stages of service planning and network design, focusing on decision-making processes and objectives. Learn about different types of transit lines, such as radial, diametrical, and circumferential, and their impact on network design. Discover key principles to optimize transit systems effectively.

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Network Design

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  1. Unit 4: Service Planning & Network Design Network Design

  2. Outline • Stages of Service Planning • Network Design • Overview • Types of Lines • Network Types

  3. Stages of service planning

  4. Service Planning Steps

  5. Service Planning Steps • Network design • Route design and stop layout

  6. Network design overview

  7. Network Design Decisions • Rare to approach from scratch • Existing route patterns & infrastructure dictate • New services complement existing services • New major investment (rail line, etc) • Significant restructuring

  8. Network Design Decisions • Geographic coverage • Temporal coverage • Connectivity (direct vs. indirect service) • Experiment with network structures and routes • Travel demand models • Link major activity centers

  9. Network Design Objectives

  10. Types of transit lines

  11. Types of Transit Lines • Radial • Diametrical • Tangential • Circumferential • Trunk with branches • Trunk with feeder • Loops on lines

  12. Radial • One terminus in city center and another outside • Sharp peaking • Can be used with branching

  13. Diametrical (through) • Connect suburbs on both sides through the city center • Inbound delays propagate

  14. Tangential (crosstown) • Run tangent to city • Common with grid patterns • Lower & less peaked demand

  15. Circumferential • Ring around city • Suburb-to-suburb connections without trip into city • More connections • No terminal time Moscow

  16. Trunk lines Trunk with branches Trunk with feeders

  17. Trunk lines Trunk with branches Trunk with feeders Each line optimized Higher performance mode on trunk More reliable Feeder to feeder transfers • Continuous service with no transfers • No transfer stations • Less terminal time

  18. Frequencies • One key to quality of service • What do branches mean for frequency?

  19. Frequencies • One key to quality of service • What do branches mean for frequency? • One of three things: • Branches have less frequent service • One branch connects into another • Vehicle separates onto both (rare)

  20. Loops on Lines • Closed circle • Usually one-way operation • Distribution in CBD Chicago

  21. Directness • Most examples so far were rail • Bus routes often deviate to serve lower densities • I, U, S, O Direct Circuitous Deviating

  22. In-class Exercise

  23. Transit network types

  24. Transit Network Types • Radial networks • Radial / circumferential networks • Rectangular or grid networks • Ubiquitous networks

  25. Radial Networks • Maximize ridership along major travel direction • Limited transfers • Extreme concentration in CBD • Unattractive for crosstowns • Less coverage area METRA in Chicago

  26. Radial / Circumferential Networks • Radial with a ring or tangent • Greater diversity of origin / destination • Greater coverage Koln, Germany

  27. Grid Networks • Large area with uniform density • Coverage • Substantial transfers

  28. Joy of Grids • Ability to travel from anywhere to anywhere • Mathematically, the most efficient manner is a grid • Why? Rectangular Spiderweb

  29. Ubiquitous Networks Coverage over all central area + Radiating out with branches into suburbs = perfect network Most complete ubiquitous network in the world: Paris!! New York is OK too.

  30. Network Issues • Radial lines with branches lead to unused capacity at ends • Different lengths / volume branches make irregular trunks • Diametrical with different loads • Triangular connections hard to schedule

  31. Conclusion • It is rare to approach network design from scratch • Existing route patterns & infrastructure dictate • New services complement existing services • Network design determines many factors of service quality

  32. Reference Materials in this lecture were taken from: • Walker, J. (2011). Human transit: How clearer thinking about public transit can enrich our communities and our lives. Island Press. • Vukan Vuchic, “Urban Transit Operations, Planning and Economics” (2005) • Mark Hickman, Fundamentals of Transportation wikibook, “Network Design & Frequency”, http://en.wikibooks.org/wiki/Fundamentals_of_Transportation/Network_Design_and_Frequency

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