# Transportation Geography and Network Science/Hub and spoke network
## The Introduction of Hub and Spoke Network

The hub-and-spoke system is the best known network system. The spokes in the network are linear services between regional terminals and the hubs. Hubs are terminals or, in railway systems, they may be marshalling yards. At the hub the transport units are transferred from one liner service to another connecting the hub with the destination terminal. Ideally, hubs are located near to the centre of gravity of transport demand. In this way detour distances and trip times between origin and destination terminals can be minimised. The dotted arrow in the picture indicates that two services (spokes) are needed to connect different regions. The total terminal-to-terminal trip time is increased because of the extra distance for the call at the hub and the time spent in the hub itself. A hub-and-spoke system is designed to combine small flows arriving and departing in different directions. In the case of railways the spokes can be of any type of liner service with any frequency <ref> Hub-and-Spoke Network

## Hub and Spoke Network in Transport

In the hub-and-spoke case for air freight or passengers, the hub airport refers to an airport with dense international and domestic routes. Passengers can easily transfer to other airports, and it also can provide an efficient, convenient and low-cost service, allowing airlines to choose it as their own route destination, allowing passengers to choose it as a transit port for transiting other airports. The hub airport is both a demand for national economic development and a demand for the development of airport enterprises.
The hub and spoke network system is an advanced form of air transport production organisation commonly used by large airlines and airports in the world today. It has multiple functions such as optimising the route structure, rationally allocating resources, enhancing the competitiveness of enterprises, and promoting airport prosperity.

## The History of Hub and Spoke Network

The Hob and Spoke airport network structure is a new route layout pattern first appeared in the United States in the 1970s. It is characterized by the fact that cities with smaller passenger flows are not directly navigable, but are all connected to a hub airport. Through the hub airport, the flight connection, transit passengers and goods are used to achieve the purpose of fast transportation of passengers and goods. The adoption of a central route structure has the following advantages for airlines:
* Optimize configuration resources and reduce operating costs. The Hub and Spoke network system is more economical than the city's route structure in terms of the number of aircraft, crew, routes and ground maintenance personnel.
* Improve the passenger load factor and load rate of aircraft and improve the economic efficiency of airlines. As the source of the feeder line is concentrated on the trunk line, it is possible to enable large and small airlines to develop their strengths and avoid weaknesses.
* Play to the rapid advantages of air transportation and improve the competitiveness of the industry. Efficient flight connections shorten travel time and increase the attractiveness of air transportation.

## Characteristics of Hub and Spoke Network
### The Main Features

The hub airport is the node of the Hub and Spoke network and the distribution centre of air passenger and cargo. Its main features are:
* A high proportion of transit business.
* Efficient flight connection capabilities.

### The Main Advantages of Establishing a Hub Airport

* Promote the increase in airport traffic and attract more flights to the airport. Increase the aeronautical and non-aeronautical revenues of the airport.
* Drive the development of the surrounding economy and related industries. For example, the development of tertiary industries such as restaurants, restaurants and tourism services.
* Created conditions for the development of the surrounding regional airport. Convenient service stimulates the demand for air transportation and brings vitality to small and medium airports.

## Limitation of Hub and Spoke Network

The hub and spoke network system has both advantages and disadvantages. The shortcoming is that if the airport capacity is too small or inefficient, the airport and route are prone to congestion and congestion, which may cause flight delays and may affect the entire network. In order to solve these problems, in addition to paying attention to improving the level of airport management, some hub airports should also pay attention to the long-term planning of the airport and gradually expand the scale of the airport. In addition, some airports have adopted the method of constructing an auxiliary airport near the hub airport to divert the passenger and cargo volume of the hub airport, which has alleviated the flight delay caused by congestion.

## Basic Conditions for Building a Hub Airport

The construction of hub airports requires certain conditions, which include the following aspects:
* Excellent buried location. That is, the location of the airport should be favourable for airlines to adopt the central route layout mode. It should consider the economy of voyage, the potential development market and the future development strategy.
* Huge air transport market and transit demand. One of the conditions for establishing a hub airport is that there should be a large market demand for air transportation and potential demand for transferring international passengers and goods. Foreign gateway airports, the proportion of international transfer passengers and goods generally to account for more than 30% of the airport throughput. High proportion of international passenger and cargo transfer is one of the important signs of hub airport.
* Complete airport transit facilities. It includes several airstrips, reasonable transfer facilities, advanced flight information system, and related supporting services.
* Strong base airline. The performance is, the capacity is sufficient, the fleet structure is reasonable and can satisfy the trunk line and the branch line need. It can have domestic and even foreign backbone airlines as partners. When one company is short of capacity, it can combine the strength of other airlines.
* Stable and coordinated relationship between departments. Close coordination among hub airports, base airlines, air traffic control, customs, border inspection and other departments.
* Loose policy and legal environment. It means that the government gives a loose operating environment, so that airlines have moderate decision-making power in the aspects of routes, fares, models and flight times, while airports enjoy certain autonomy in the design process, charging standards and operating projects.

## Point-to-Point versus Hub-and-Spoke Networks

A point-to-point network connects directly a set of locations without any interruption of services (e.g. pick up or drop off) even if the route itself may not be direct. A (pure) hub-and-spoke network connects every location through a single intermediary location called a hub. Hub-and-spoke, as a network structure, allows for a greater flexibility within the transport system through a concentration of flows.
Many transportation services have adapted to include a hub-and-spoke structure. The most common examples involve air passenger and freight services which have developed global, national and regional hubs, such as those used by parcel carriers such as UPS.

## Discussion
### Some Possible Issues of Hub and Spoke Network

* Some airports and airlines have not reached a consensus on the construction of aviation hubs. In essence, the construction of an aviation hub is a development strategy of airlines. It is an effective means for air transport enterprises to obtain competitive advantages and survive and develop in a competitive environment. However, due to the limitation of subjective and objective conditions, some domestic airlines have little enthusiasm and an insufficient understanding of the construction of aviation hubs.
* Transfer support capacity is insufficient. Although some governments have transformed some airports so that they have a certain transfer capacity, they cannot fundamentally meet the needs of future airport development. To improve the airport transit support capacity, it is necessary to design the transit process with the concept of hub aviation, improve the capacity of runway, apron, terminal building and boarding gate, strengthen the scientific management of airspace, improve flight connection capacity and shorten the transit time of passengers.
* Base airline scale needs to be guaranteed. To implement a hub aviation system, airports must rely on base airlines. Throughout the world's large hub airports, the business volume of its base airlines generally accounts for more than 50% of the airport's business volume. For example, American airlines accounted for 73.5% of its Atlanta hub flights, northwest airlines accounted for 79.8% of its Detroit hub flights, and Lufthansa accounted for 60.8% of its Frankfurt hub flights. Air France handles more than 52 per cent of passenger and cargo traffic at its Paris hub.

## Conclusion

In a word, the hub and spoke network system is an advanced mode of air transport organization. It is not only necessary but also urgent to continue the development of the hub aviation system. As the hub and spoke network is a complex and huge system project, it requires the cooperation of government departments at all levels, airlines, airports and other relevant units to create conditions, so as to promote the development of the hub and spoke network system.
Generally speaking, many transportation services have adapted to include a hub-and-spoke structure. The most common examples involve air passenger and freight services which have developed global, national and regional hubs, such as those used by parcel carriers such as UPS, FedEx and DHL. However, potential disadvantages may also occur such as additional transshipment as fewer point-to-point services are offered, which for some connections may involve delays and potential congestion as the hub becomes the major point of transshipment.

## Reference

* https://gc21.giz.de/ibt/en/opt/site/ilt/ibt/regionalportale/sadc/inhalt/logistics/module_01/231_hubandspoke_network.html [2019-Sep-03]