Published literature on transportation networks suggests that one of the main features of a network is mobility; defined as the ease of travelling from one location to another within the same network (El–Geneidy and Levinson, 2011; Paleari et al, 2010). A number of studies have concluded that everything else being equal, users of transportation systems prefer shorter, faster or more generally less costly paths (Cento, 2008; Bell and Lida, 1997; Kanafani, 1983). In air travel it is argued that travellers prefer direct flights. When multinational companies make investment location decisions, they want to know not only how many destinations they can fly to from a certain airport, but also how far these destinations are and, therefore, how long the flight would take and how much it would cost (Goedeking, 2010; Cento, 2008).
One can conclude that from the air travelers’ point of view, a regional aviation network is said to be efficient when it;
Can facilitate access to valued destinations
Offers the shortest possible paths and
Offers less costly alternative paths between airports
Passengers generally desire frequent, direct or non-stop and reasonably priced connections between each city-pair in the network (Mason, 2000). Where such connections are not achievable between all city-pairs, an efficient network still facilitates rapid connections through third cities. For a service to be reasonably priced, published literature on transport economics state that market competition must exist (Morrell, 2007).
Air transport literature is replete with countless measures by which the features of efficient networks have been described. Some of the measures that appear consistently in many studies on transportation networks are connectivity, accessibility, circuity and competitiveness.
2.5.1 Network connectivity
Sokol (2009) defines connectivity as a measure of the degree to which a network as a whole or its parts is internally connected or linked. This, he argues, can be judged by “the ease with which people, materials and information can be moved from one location to another, within and between regions.” In air transport, connectivity relates to the degree to which people are able to travel to other cities through airline services (Chou, 1993). Connectivity is desirable as it presents a wide range of destination choices for both passengers and cargo. In SADC, as in any other part of the world, higher network connectivity is desirable as it eases the movement of persons, goods, equipment and services; a feature essential for regional economic and social integration.
2.5.2 Network accessibility
Various definitions exist for this term whose origins Handy and Niemier (1997) trace to Hansen (1959). According to Handy and Niemier (1997) accessibility relates to the potential of opportunities for interaction. Reggiani and Martin
(2011) suggest that accessibility measures the propensity of economic actors or users to reach certain economic activities or destinations. Various authors describe accessibility as the measure of the ease with which one place can be accessed or reached from another location, or to provide access to other locations (Chou, 1993; Sokol, 2009; Wachs and Kumagai, 1973; Rodrigue et al, 2009; Reynolds-Feighan and McLay, 2006). In air transport accessibility is measured by how easily one airport can be reached from all other airports in the same network. Accessibility is desirable as it offers cities opportunities for social and economic interaction and the potential for growth and development. For SADC higher accessibility is ideal as it offers cities the opportunity to receive significant flows of visitors, trade and investment.
2.5.3 Network circuity
Circuity relates to the ability to move independently between a region’s major economic centres (e.g. going from airport A to C, without having to go through airport B). In air transport, circuity is measured by the degree to which the design of the network overcomes the friction of distance. Friction is defined as the difficulty of moving a volume (passengers or goods) per unit of distance Rodrigue et al (2009). According to transportation literature, distance determines the quantity of interaction between places. Distance is considered an impediment to spatial interactions because as distance increases so does cost in terms of time and money.
The qualities of direct and indirect connections in an air transport network are not the same (De Wit et al, 2009). Passengers using indirect connections between airports experience additional costs due to longer travel times as a result of detour distance. Reduced circuity lowers travel costs in terms of time and money. As movement becomes less costly demand for air travel is often stimulated. Reduced circuity is therefore the preferred option in the developing region of SADC as it lessens travel costs and would in turn stimulate demand for air travel.
2.5.4 Network competitiveness
The ease with which passengers or cargo are able to move within an air transport network cannot be judged just by the number of connections that exist between the major economic centres because the number of airlines serving the network determine the quality of the connections.
Market concentration is considered a key determinant of conduct and performance of airlines on city-pairs. In economic theory, market concentration is a measure of the number and size distribution of sellers (Bergeijk, 1996). Arguing that high levels of concentration advance the leverage sellers have vis- a-vis buyers, economists posit the differences in market concentration distinguish the theoretical models of perfect competition, oligopoly and monopoly. Market concentration is high when the industry is dominated by a small number of large firms. In air transport, an efficient network fosters airline competition. In the absence of competition the incentive to increase services, innovate and even lower fares is assumed to be absent (Bowen, 2002). For SADC, a region defined by low disposables incomes, a network characterised by a sizeable number of competitors is desirable as competition amongst airlines would lower fares, encourage innovative products, stimulate demand and ultimately improve the performance of the airlines serving the network. As air travel is a derived demand a higher number of frequencies would likely allow travellers particularly business traffic to pick convenient flights.
However the political will of national governments plays a significant role in establishing, maintaining and changing the geography of the regional civil aviation network to ensure these four features (connectivity, accessibility, circuity and a competitive market) exist. It is for this reason that IATA (2012) proposes deeper and wider air transport liberalisation as the appropriate instrument by which policy makers could develop efficient civil aviation networks.