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Designing Networks For Life

How a Hub-and-Spoke Model Could Improve Metro Rail Transit

This article on the airline hub-and-spoke model as one type of network as well as its potential application to the design of metro rail transits offer some new and interesting perspectives on the concept of networks we learn in lecture. The nodes now represent countries, cities, or even smaller regions instead of people. Among them, there can be influential nodes that may represent capital cities or relatively more developed regions (where the populations are usually larger, too). Besides, the network concerns the thickness, the density of the flows, of the edges, adding a new dimension to the general graph. Last but not least, the article attempts to evaluate the network by taking into account the efficiency of the existing connections. In the case of the airline network, the cost of flight plays an important part in determining the edges. In other words, since the cost of a flight is high, a flight with very few passengers seems uneconomical, and an edge between two “marginal” nodes may be of little value. In reality, in addition to airline maps, when we look at the maps of railways, trains, and buses, we can also find similar patterns and derive similar inferences. Even more, the network is by no means static; new connections can be created or destroyed contingent on external environments or the nature of nodes. A classic example is that during holidays there tend to be more flights, or edges, connecting previously disconnected nodes to mitigate the traffic density. As a result, the dynamics of networks and their rich interpretations are of great value to network designs.

When considering networks that are constructed in real life for various purposes, a central issue is concerned with designing a network that works out most efficiently and effectively. Efficiency could be defined in terms of economy, user experience, etc. In class, we looked at an example that adding a traffic lane will increase traffic, which seems contrary to our intuition when we try to come up with a solution to traffic congestion. The implication of this instance is that for a well-developed network, the quality and efficiency of edges might outweigh the quantity of edges. Another important aspect of the network design is to effectively combine a variety of network types, bringing together nodes and edges of various characteristics, to create a synergy effect. With regards to transportation, this attempt can be achieved by combining various means of transportation to connect long-distance routes. For example, bus stops can be placed near railway stations; railway stations can be connected to airports.

Another interesting aspect we could look at is how transportation can be related to the development of a country or city. Does the development of the transportation system reflect or facilitate regional development? Or does these two types of development happen simultaneously, similar to a symbiotic relationship? On one hand, because of efforts to create a network, more isolated components could be brought together, benefiting from concerted contribution and the network effect; in this sense, transportation development facilitates regional development. On the other hand, it is also because of the uneven regional development that some “nodes” appear more influential and thus more edges are built on them; as a result, the nodes and their traffic density can reflect regional development. Thinking of nodes and edges in terms of what they stand for in reality can shed more light on the significance of networks to our lives.


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