Intermodal production systems

In order to supply cost-competitive transportation services intermodal production systems are designed to achieve the maximum possible capacity load factor. Every production system selected by an operator will reflect the specific market situation particularly as concerns the assessment of the potential market share, the type of cargo and customers, and the regularity or volatility of transport flows. Against this background we distinguish two main categories of production systems for intermodal transport:

• A full-trainload production system can be employed on trade lanes that provide for sufficient point-to-point volumes to operate a regular service. Shipments are consolidated at the point of origin and carried to the final destination avoiding any intermediate handling of the train for loading, unloading or transhipment. In intermodal transport, full-trainload services are usually terminal-to-terminal journeys.
• If the volume of shipments between origin and destination areas falls short of the economic threshold of full trains less-than-trainload production systems have to be implemented. They imply that the volume of two or more O/D trade lanes will be bundled and/or distributed at intermediate handling points by applying various technologies described below. The key objective is to generate full trainloads on every single section of the rail service even if the shipments travel on various routes. Since every action to consolidate volumes produces additional handling cost and consumes time the intermodal operator is required to assess whether the outcome is still competitive and the service acceptable for customers.

While full-trainload systems could be operated as stand alone services less-than-trainload production schemes necessarily are network systems to a certain extent.

Field of employment	Production system
Full-trainload O/D lanes	Direct train Shuttle train
Less-than-trainload O/D lanes	Y-shuttle train Liner train Group train Turntable traffic Gateway traffic Megahub/Mainhub production Mixed intermodal/conventional traffic

Direct train

For a direct train operation a set of intermodal wagons to be loaded is formed at the departure terminal. This train set runs straightforward to the arrival terminal without any manipulation of wagons or shipments. For the return journey the intermodal operator may employ the same wagon set but he might also adapt it to the specific needs of the route concerning the demand for transportation, the pattern of customers’ loading units or the shipment weights. Theoretically, the wagon set of a direct train could be customized for every single trip to respond to requirements. However, intermodal operators are reluctant to change the composition to avoid shunting cost and minimize the reserve stock of wagons at the terminals that, if they couldn’t be deployed on other services, would stand idle.

According to operators’ experience a trade lane, which shall be served by direct trains at least every working day both ways, requires for an annual O/D market volume of about 150,000 to 200,000 tonnes. Consequently, direct trains are most suitable for connecting agglomerations, centres of industrial production and container ports with major inland locations. They are equally used for domestic and international traffic, in container hinterland and continental transport. The direct train production is one of the most often employed systems in combined transport in Europe because it is a very efficient scheme that avoids train manipulation as much as possible.

Shuttle train

The shuttle train is an improved version of the direct train production. Like a direct train it operates point-to-point without intermediate handling operations. Unlike a common direct train, however, the shuttle train is commuting between two intermodal terminals with a dedicated set of wagons. Operationally, the train must only be manipulated if damaged wagons need to be replaced.

An economic shuttle train system just like a direct train requires for an annual transport volume of about 150,000 to 200,000 tonnes. Since the wagon composition of a shuttle train is due to be maintained for a longer period – from one month up to one year - prior to the implementation of this scheme, the intermodal operator will have analyzed the market thoroughly whether the patterns of demand are rather stable and predictable.
Currently, shuttle trains are primarily deployed on domestic and international continental services to link long-standing areas of industrial production. However, they are rather seldom used in container hinterland transport since the flows are less stable and balanced.

Y-shuttle train

A Y-shuttle train is composed of two and sometimes even three train sets with dedicated wagons, which though departing from separate intermodal terminals are bound for the same destination. The train sets are assembled at either a train station providing for appropriate shunting tracks or a marshalling yard. One version of the Y-shuttle shows the typical funnel-shape: The two train sets start from terminals with a different catchment area and are merged at an appropriate node in the rail network. On the return trip the same wagons are employed but the production process is organized the other way round: at the interim node the full train is split up into two sets, which then are moved to the intermodal terminals in question.
More typically is the second “in-line production” version of the Y-shuttle train: one train set departs from the first terminal and the other half-train is attached to it in the neighbourhood of the second terminal located on the route to the arrival terminal. This scheme in fact is not so different from a liner train production.

In order to avoid sub-optimum employment of train capacity, which might lead to non-competitive operational cost per shipment, it is paramount that the distance between the two terminals is short compared to the total transport route. If this prerequisite is matched the Y-shuttle production can universally be used if the intermodal operator:

• seeks to link an economic centre with two or three medium-size economic areas;
• is scheduled to inaugurate new direct train services but prefers to reduce the economic risk in the initial phase by bundling two or more freight markets;
• is testing which of the local markets respond more positively to the new service.

The Y-shuttle production system is often employed particularly on domestic services of both categories of combined transport services and also on international continental services. According to the results of our market survey, however, it is rather rarely performed in the original meaning of the word “shuttle”. In many cases the wagon sets are not completely dedicated, and the train parameters allocated to the terminals involved in the system are subject to changes as well.

Liner train

This type of production system bundles the volumes of intermodal shipments originating in two or more terminals that are located in a line, and carries them to a destination terminal, and vice versa.
In the “classical” meaning of liner train operations a full train set of wagons independent of their loading status is starting at the first terminal of departure, enters the second terminal where loading units are both loaded and – if requested – unloaded, and continues to its final destination provided that the train doesn’t call at a third liner terminal. For a very long time such a type of liner train was only a theoretic concept, however, it hasn’t been implemented for economic and technological reasons. Since recently a blueprint exists: liner trains starting at the Maasvlakte container terminal in Rotterdam call at the RSC terminal and carry on to several international locations.
Another apparently more common variant sees the liner train not pulling into the intermediate terminal for transhipping loading units. Instead the shipments have already been loaded on a group of wagons, which is then attached to the starting set. This type of liner train production resembles the “false” Y-shuttle. Only if also a wagon set with shipments from the liner train production.

Basically, the liner train production system appears to be suitable for serving locations with a large total market potential for combined transport, which, however, is split into several less-than-trainload trade lanes, such as regions with a polycentric pattern of economic activity. In order to achieve a high capacity load factor over the total distance of the service the amount of shipments that get off the train and those that embark it at interim terminals must be highly balanced. Most of the time, the reality of transport economics is different. Owing to this lack of economic performance and technological barriers – only very few intermodal terminals provide for a direct and fast access to the main line –.the liner train production system, for the time being, hasn’t spread largely.

Group train

In the most elementary case the group train system comprises two trains departing from different intermodal terminals. Each of them consists of two groups of wagons bound for two terminals of destination. The trains meet at a node in the rail network that is playing the role of a turnpike for this system. Here the wagon groups are interchanged between the trains by preferably employing the long-distance locomotives in order to set up single-destination trains for the terminals involved. Therefore it is of utmost importance that, at the departure terminals, the wagons sets are always put in such a sequence to enable a fast swap at the turnpike. The system works the same way in both directions.

The group train system was likely to be the most employed production scheme in combined transport in Europe until the mid-90s. It was the backbone both of domestic networks and international services. This production system was also related to the business model and the commercial relationships between railway undertakings and intermodal operators at that time. The railways controlled and run the system more or less at their own risk whereas operators either booked a certain train capacity in advance or purchased on a per wagon basis.
Over the years group trains lost their importance with the enforcement of block train services and the growth of combined traffic volumes allowing for operating more efficient direct trains. Notwithstanding, some intermodal services currently are based on group train operations involving even three or more trains, which are interlinked at turnpikes. Group trains enable intermodal operators to serve connections between medium- and even small-size economic areas.

Turntable traffic

Even more than the group train production the turntable system allows for bundling the volumes of numerous trade lanes and connecting a couple of areas and intermodal termi-nals. The amount of trains involved in such a network of intermodal services is depending on the freight market affected and the geographical situation. What is a distinctive feature of turntable operations, unlike the other production systems described above, is that it is based not on end-to-end or terminal-to-terminal trains but on two separate train services, which are linked via a turntable that is a shunting yard.
At the departure terminals intermodal trains are loaded largely unsorted with shipments bound for many places. At the shunting yard trains can be handled in two different ways. Inbound trains can be split up completely and the wagons are resorted by gravity-shunting to assemble new outbound trains – just like in single-wagon traffic. Alternatively, single wagons or groups of wagons are moved and interchanged between the trains – like in the group train production. In fact both procedures might also be employed simultaneously. The outbound trains to the final destinations must not necessarily be direct services though, in practice, they often are.

A typical representative of the turntable system has been Transfracht’s Albatros domestic network in Germany with the turntable Maschen.

Gateway traffic

At first sight, the approach and the workflow organization of a gateway production may look like the turntable traffic:

• The gateway system is composed of two separate train services.
• The trains are interlinked at a node.
• The trains starting at the departure terminals may be carrying shipments bound for various destinations.
• Outbound trains leaving the node are very often direct or even shuttle services.

The key distinction between the gateway system and the turntable traffic, and what makes the system unique and only applicable in combined transport is that the turntable of the gateway system is an intermodal terminal. Since inbound and outbound services at the gateway terminal are used to rely on separated rail traction services and train sets, inbound trains must be completely discharged. What is also a distinctive feature is that inbound trains to the gateway terminal move both shipments for the local market, which are due to be picked up by road vehicles for delivery, and shipments, which must be carried on. The latter units are transhipped to the trains bound for the final destination terminals. In many cases a direct move will not be possible owing to distinguished arrival and departure times of services involved. The units must then be stored intermediately at the terminal yard. The gateway concept successfully is operating both ways. Whereas, however, the trains in one direction are composed of shipments for several destinations they carry almost only dedicated shipments in the opposite direction.
The gateway system has been introduced by the intermodal operator Hupac. Currently, many other companies such as Cemat and Kombiverkehr have adopted this scheme and extended its scope of application. Initially the gateway production was intended to connect domestic and international intermodal services on the continental freight market. It particularly enabled operators to supply competitive international services to medium-sized economic areas. Meanwhile the system has also been spread to be employed in domestic networks and for integrating maritime container transports.

Megahub/Mainhub production

The mainhub or megahub production system can be considered as an even more sophis-ticated gateway concept. What is comparable is that, from one end of the transport chain, intermodal trains leave with shipments, which since they are bound for various destination terminals will be resorted at an intermediate hub terminal. The hub production, however, has a couple of distinctive components:

• In the first place, it is based on through-train sets from origin to destination terminals, not on two separate traction schemes in and out the hub.
• While incoming trains always feature shipments with a variety of final destinations, outbound trains are used to collect units for a single terminal (direct service) or at maximum two sites (liner service).
• All trains that are dedicated to specific O/D intermodal services must arrive at the hub terminal as a “bundle” within a tight period of time (“time-window”) to enable transhipping intermodal loading units fast, cost-effective and directly between trains and avoiding interim storage. Usually, every train will operate on a defined route with a defined destination. All those shipments that are bound for this destination but arrive on another train must be transhipped and assembled with loading units of other origins but the same destination.
• A hub terminal must not absolutely be dedicated to this sorting function. It could also perform road/rail handlings for local shipments. However, it is paramount that the time-critical transhipments are prioritized.

Compared to the gateway concept the mainhub or megahub production system enables to achieve faster transit times, which would allow for serving less-than-trainload lanes over medium distances at a road-competitive schedule. There are large potentials especially on domestic freight markets that could be opened up for combined transportation.
In fact, the Belgian operator Interferry Boats (IfB) is employing such a system at its main-hub terminal in Antwerpen designed to serve especially national routes of container hinterland traffic. The trains that depart from various quays are more or less unsorted concerning the destination of the containers. The mainhub terminal cares for transhipping containers between a bundle of six to seven trains, which are in the handling area at the same time, and producing dedicated trains as far as possible.
In Germany, the intermodal stakeholders under the lead of DB Netz are seeking to build a megahub terminal in the vicinity of Hannover, which is a prerequisite for implementing a production system that should primarily be geared towards the needs of domestic freight both for the continental and maritime business.
The largest challenge for this type of production system is to ensure a high reliability of all trains belonging to a “bundle” handled simultaneously at the hub terminal. Owing to the small time frame for transhipments, a delay of only one train would have a negative impact on all other trains of the bundle.

Mixed intermodal/conventional traffic

The combination of intermodal shipments and conventional rail wagons calls for establishing one consolidation and one distribution centre in the rail network since generally both rail freight services will depart from and arrive at different locations. Conventional wagons are usually loaded and discharged at rail sidings, combined transport travels between terminals. Between the two nodes the cargo is carried together. Economically, it is paramount that the distances between the loading/unloading stations and the nodes are short compared to the total rail journey.

Two fields of deployment for the mixed production system have been identified:

• On inter-industrial trade lanes between two production facilities or on routes from one manufacturer to a big customer, various commodities come up such as packed and bulk goods, which are more suitable either for road and intermodal services or for conventional wagons. Instead of running separate rail freight services the idea is to combine them on the trunk haul. Such production schemes are used particularly in the chemical industry as well as in the automotive industry.
• Another approach advances from the assumption that, in each direction, the “strength” of one type of rail freight is compensating for the “deficit” of the other. Conventional wagonload traffic is unbalanced in most cases, loaded one way and empty return. In contrast to that the capacity of intermodal trains is employed rather evenly on round-trips at least as concerns the amount of units. If, however, the capacity of an intermodal service were underemployed in terms of weight on the direction where conventional wagons are full the combination of both services would bring about a benefit for each of them.