A Supply Model for Maritime Terminal of Intermodal Transport
A G Cartisano, F Russo, University of Reggio Calabria, IT
Nowadays, freight transport plays an important role in the transport system  , insofar as it is a fundamental element for the economic development of an area and a country in general . Knowledge of the effect of the various factors upon freight transport times and costs is essential in different sectors . In the context of strategic planning, such knowledge allows us to appraise different development policies of the various modes, analyzing their respective economic benefits.
In operational context, knowledge of the various factors allows us to determine cost and performance functions. In Italy over 80% of freight is transported by road although the country has over 7400 km of coastline that are well suited to short-sea shipping . The most promising area of development is the tendency to view the Mediterranean as a fulcrum in the world maritime scenario. In particular, container traffic through the port systems of southern Europe have seen a much higher growth rate (+80%) than in those of northern Europe (27.6%) in the period of reference from 1995 to 1998. Ports and freight villages are viewed as centres of transport and freight interchange, equipped to integrate traditional road transport, using sea and rail for long routes  .The ports are organized as freight interchange centres: they are equipped to integrate with road transport for the initial and final links, and use sea and rail routes for long distances. The elements that form an integrated freight transport system, whether it be multimodal (freight transfer by two or more transport systems), complex monomodal (freight transfer that uses only one mode of transport but with different vehicles) or intermodal (freight transfer that uses more than one transport mode but using the same container) or combined definited also piggy-back transport (intermodal transport by means of container, swap body or semi-trailer, and using road for final haulage, and rail or sea for the intermediate leg), can be aggregated into three categories: Loading Unit (UL); Movement Units (UM); Transportation Units (UT). The freight transport systems that use more than one mode have acquired greater importance as they lead to a total reduction in costs
The freight transport systems that use more than one mode have acquired greater importance as they lead to a total reduction in costs. One of the main hubs of the intermodal system is the port because of the modal change involved. It is thus necessary to have a supply model that allows, to estimate in the planning phase, cost and performance of the specific hub in the transport system.
In the full paper a method is introduced to model the road-sea intermodal system. The connecting infrastructures, namely the port systems, are analysed, using a method proposed in literature. Finally performance functions are specified and calibrated in relation to the different types of terminals.
In the case of specialised ships, in multipurpose ports, the transport system may be represented according to the type of ship using graph theory. Transport services can be represented through a run-based approach using a space-time or diachronic graph ??. The diachronic graph consists of three different subgraphs in which each node has an explicit time coordinate: a service subgraph ?g, demand subgraph ?d and access/egress subgraph ?ae. Finally, the global diachronic graph ?? is obtained through (? = ?g ? ?d ? ?ae) in which links connecting the three sub-graphs are properly adopted. In the graph we can define the link load and cost vectors f and c, the path load and cost vectors h and g, and the link-path incidence matrix ?, obtaining the classical equations
f = ? h
g = ?? c + gNA
Representation of a multipurpose port is not as straightforward as for a specialised container terminal, given the great variety of freight involved. Indeed, a specification of operations conducted in the port may be associated to each type of ship, and hence of good.
In this paper different types of ships are considered: those support transport with trucks or semi-trailers, namely Ro-Ro ferries with single and double-access, and Lo-Lo feeder or liner ships.
Data were gathered from the port of Catania, with subsequent surveys in the ports of Palermo and Villa San Giovanni (Straits of Messina). The shipping traffic observed concerns tree types: Ro-Ro ferries (short and long routes) and Lo-Lo feeder ships. As regards the former, the times were recorded for each manoeuvre (2,548 in all) of loading and unloading of vehicles for 38 ferries arriving in port, while 2,692 times were recorded for 29 feeder ships arriving in port. The calibrations have been performed by means of linear regression.
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