In this page I want to give an overview of what types of transit networks that there are. Since the original page became quite long, each network category has a separate post which discusses the types of transit networks together with fictional example for each. Fictional examples are drawn again on the 1905 Königsberg map background map, vectorized by Wikipedia user Furfur. This list builds on the previous list Route Types: Geometry, which defines the terminology for different types of public transportation routes. Hopefully by defining types of networks my exercise can help persons easily understand differences and support a discussion.
Here is a list of network recipes, which one fits best to your circumstances?
My effort is a result of my frustration of not finding a comprehensive detailed list of network types. There are many terms for the same type of network and there are several overviews, Vuchic  defines Regular Transit (Trunk Line & Feeder) and Commuter Transit (Feeders with a Trunk Section). Steierwald and Künne  define Radial Networks (Polar), Ring Networks (Circular Minimal) and Raster Networks (Grid, both square and triangular) and then they differentiate between Direct Network, and Transfer Network before discussing service types (On-Demand versus Scheduled). Elsner  discusses 6 different Polar Networks; Polar, Tri-Polar, Trunk-Line Tri-Polar, Tri-Polar with a (Soviet) Triangle, Polar trunk lines with inner and outer ring (English) and Tri-Polar with middle and outer ring. Höfler  defined networks according to their layout, scheduling and stations. Constantine Pitzen drew theoretical networks for different service types in 2000. A. Bertaud  (Metropolis (2001)) defined Monocentric and Polycentric, and Organized and Disorganized.
Most classifications focus on the difference between Polar Networks and Grid Networks, as visualized in the graphic above by Szarkowski of EnvisionBaltimore. My terminology is mainly based on the excellent classification by Graf , who defined networks from a logistics point of view.
This is the most simple type of network and consists of one route (R=1) that connects all serviced stations. Every station (N) is connected to two others by a route segment (RS) or one other station if it is the start-point or final destination of a non-circular route. This type of network is the travelling salesman problem.
RS = N or RS = N-1 and R=1
For more details on Minimal Transit Networks read further here.
Vuchic defined two types of Linear Networks, Trunk Line with Feeder and Feeders with Trunk Section. Below are four examples of Linear Feeder Networks that differentiate from each other by what kind of feeder lines they incorporate. And further below are two Trunk Network one originating from a single point of interest and the other with a trunk section that connect several points of interest.
For more details on Linear Transit Networks read further here (soon).
A Direct Network (or Point-to-Point Network) connects ever single station (N) to every other single station by a route (R) which has only one route segment (RS).
The detour ratio of this kind of service is 1:1 making it attractive to potential passengers but usually expensive and increasingly complex. With a increase of destinations serviced, managing to fill a transportation vehicles to it’s capacity becomes increasingly difficult, resulting that most Direct Networks have either three to a maximum of five destinations or have vehicles with a small passenger capacity and flexible schedules and routes (e.g. taxi services) as defined by Pitzen (2000 page 58).
The simplification of a Direct Network so that every outer station (Νs) save 1 (ΣΝs=ΣN-1) is connected to one central station (Hub) via a route (R) (Spoke) which has only one route segment (RS) is known as a Hub and Spoke Network.
For more details on Direct Transit Networks read further here.
Flexible Direct Networks
Named after the coordinate system, by a Polar Transit Network radiates out from the town centre in all direction with the possible addition of tangential and circumferential routes that follow a path around the town centre. The vast majority of public transit networks of individual cities are some iteration of a polar network. The main planning differences are
- how to organize transfers in the city centre,
- radial routes that end in the centre versus diameter routes that intersect the city centre.
- circumferential routes versus tangential routes versus radial/diameter routes that arc.
For more details on Polar Transit Networks read further here (soon).
A Grid Transit Network is made up of a system of parallel routes that either run in two directions (e.g. North-South & East-West) or three directions (e.g NNE-SSW, NNW-SSE & E-W) forming squares or triangles (and trapezoids) as defined by Steierwald . Many cities with a planed street grid adopt this type of transit network and there are many cities with irregular street patterns that do as well. A further Diffuse Grid Network was defined by Bertaud  and theoretically and four direction network could also exist (e.g N-S, E-W, NE-SW & NW-SE) that could be implemented for cities that were built with such a street layout (see for example Washington, D.C.).
For more details on Grid Transit Networks read further here (soon).
This is a theoretical list and every public transportation network, in real life is different and in some way or another, a hybrid. Disagree with the list? Is an important theoretical or real life example missing? The Spiral Network? I welcome your critique.
Literature and Further Reading:
-  Urban Transit – Systems and Technology (2007), Vukan R. Vuchic see also Urban Public Transportation – Systems and Technology (1981)
-  Stadtverkehrsplanung – Grundlagen, Methoden, Ziele (1994), Gerd Steierwald & Hans Dieter Künne
-  Handbuch für den Öffentlichen Personen Nahverkehr (1980), Otto Elsner
-  Öffentlicher Verkehr und PKW im Systemvergleich (2002), Leonhard Höfler
-  The Geography of Transport Systems (2006), this book is a result of a project headed by Jean-Paul Rodrigue since 1997. Most of the book is freely available and worth reading under the website transportgeography.org .
-  Netzstrukturplanung: ein Ansatz zur Optimierung von Transportnetzen (2000), Hans-Werner Graf also available here. (in German)(in German)
- Jerret Walker wrote an article about the advantages of Square Grid Networks versus Polar Networks. Recently Alon Levy has argued in favour of Polar Networks, discussing the reasons why one should appreciate such a network.
- Empfehlungen für die Anlage von Erschließungsstraßen by the Forschungsgesellschaft für Straßen- und Verkehrswesen (FGSV). (in German) the
- MotionDigest has reviewed several vehicles that can be used in On Demand Direct Networks.