EVALUACIÓN DE LOS RESULTADOS Y DEL PROCESO DE ENSEÑANZA

Routing is the process of selecting paths along which to send network traffic and can be applied to a variety of scenarios including electronic data networks and transportation networks. Networks are implemented for all transportation modes and are defined as a collection of points and lines joining these points (Bazargan, 2004).

Figure 5 represents an example of a network.

Figure 5 - Basic Elements of a Network (Bazargan, 2004)

Networks and routing can have a significant impact on the financial prosperity of the user, therefore careful and analytical planning is required to ensure the network chosen best suits the business model of the organisation.

Several different transportation models exist and can be seen in various forms throughout all modes of transportation. There are two main models, which are:

 Point to Point

 Hub Network (Hub to Spoke)

Nodes

3.1.1 Point to Point

The point-to-point network model, sometimes referred to as the fully connected network theoretically is a network linking every city on a route to every other instead of going through a central hub. In reality not every city can be

connected to every other.

Figure 6 below shows an example of a point to point model.

Figure 6 - Example of Point-Point and Hub Network Models (Bazargan, 2004) The point-to-point model is mainly applied to rail networks and a minority of airlines. Before deregulation in the 1970s, the point to point model was used by the majority of airlines particularly in the US. The issue of network topology was largely ignored and routes were constructed on a demand like basis. The result was that the carrier would have a network pattern similar to that of Figure 6 and with no focal point (hub), the ability to provide an integrated network was limited.

For example a customer wishing to travel from D to G would have to travel in stages (D-F-I-G). The point to point model particularly when used by airlines, is seen as particularly inefficient. The system does not mean that hubs are neglected, however passengers would often have to change between carriers and aircraft. The point to point model is far more suited to rail transportation where more regional travel is used opposed to trips exceeding 1000km more

I

F G

H B

A C

D

E

commonly associated with aviation. Figure 7 shows an example of a US rail network, which uses the point to point model.

Figure 7 - Point to Point Model Example of 1962 US Rail Network (New World Economics, 2010)

3.1.2 Hub to Spoke

The point-to-point model is the predominately used by maritime and rail transportation, however in aviation it is seen as inefficient for the majority of airlines. The hub and spoke network is the model of choice for airlines due to the efficiencies that it brings. Hub and spoke has been the historic choice for European Airlines and has been adopted by many of the US carriers following deregulation. Figure 8 below illustrates why the hub model is so attractive to carriers.

Figure 8 - Point to Point and Hub-Spoke Comparison

In the examples shown above, if the circles are assumed to be five cities or airports then by using the hub and spoke model, the number of routes is reduced to 4 instead of the 10 used in the point to point model. This is achieved simply by adding a centralized hub (represented by the red square).

Hub and spoke networks offer significant advantages over the point to point model. Passengers will still often be required to change services/aircraft to complete their journeys, however the hub to spoke strategy works by coordinating the arrival and departure of a large number of services in a narrow time window. Travel times for some passengers will be increased, however fares are traditionally lower and the potential combinations available to any destination are expanded significantly.

Within aviation, the economies available to carriers are considerable. Airlines initially serve routes with larger aircraft due to increased demand but with less intensity, resulting in lower operating costs per passenger and reduced fares.

As the fares continue reducing, the demand will increase requiring even larger aircraft, increased frequency and newer routes. This strategy is one of the reasons for aviation’s rapid growth, enabling greater numbers of the world population access to affordable air transport.

The structure of an airline network is also of great significance both for passenger convenience and also for the socioeconomic condition of the areas covered by the network.

HUB

POINT TO POINT HUB AND SPOKE

3.1.3 Routing options available to operators

As mentioned previously, the two main transportation models utilised by commercial airlines are the point-to-point transit (PPT) and spoke to hub distribution (SHD) systems. Both systems have their own benefits and drawbacks, however these mainly focus on economic and sociological issues with negligible thought regarding the environmental impacts of both models.

Spoke and hub distribution is the system currently used by the majority of airlines. It offers the operator many benefits including the centralisation of control to one hub and the likelihood of higher passenger demand and increased LF when compared to smaller ‘non hub’ airports. British Airways (BA) for example operates to all six continents from its main hub London Heathrow (LHR). The majority of BA’s routes are direct to the destination apart from obvious exceptions such as Australia and South America due to distance limitations.

Point-to-point transit systems are less commonly used although they can offer some unique benefits, particularly for passengers who are not required to commute to the central hub. US operator Southwest Airlines uses the system throughout its network (Aris, 2008).

Both networks offer different business models to operators mainly focusing on economic efficiency, however the environmental impact is less discussed.

Therefore this paper will propose and examine a third conceptual transportation model, ‘multiple hub-spoke’.