THE INTERMODAL TRANSPORTATION OF SEMITRAILERS

The paper focuses on intermodal transportation systems for semitrailers in Europe. Transportation of semitrailers by rail is a good alternative to direct road transport. In the paper, individual systems are presented and their characteristics are explained. The characteristics of individual transportation systems are the inputs into the WSA and the TOPSIS methods. The results of the methods answers the question which semitrailer transportation system is the most suitable (beneficial) for trucking companies today. The paper may be a source of information for state authorities, trucking companies, intermodal transportation operators and terminal operators.


INTRODUCTION
Intermodal transportation is an important measure for sustainable development and -more specificallyfor sustainable logistics/transport. It is beneficial regarding environmental protection and has potential for modal-shift from road transport to rail (and water) transport. Current situation of modal-split on European freight transport market is: 75.3% road transport, 18.7% rail transport and 6% inland waterway transport (Eurostat, 2020). The data are for the year 2018. The share of transport modes is counted according to transport performance (in tonne-kilometres, tkm) There is an effort to use modal-shift tools to improve the modal-split -i.e. to encourage greater use of ecological and safer transport modes (rail and water transport) and decrease the share of road transport. Among hereinbefore mentioned modal-shift tools, the intermodal transportation belong.
Intermodal transportation has two main ranges -accompanied and unaccompanied. Accompanied intermodal transportation systems are transporting whole road vehicles (usually vehicle combinations) and their drivers. Among these systems belong: RO-LA (German: Rollende Landstrasse; Rolling Road), LeShuttle-Freight (operated in Eurotunnel) and ferries. Unaccompanied intermodal transportation systems are transporting only intermodal loading units (ILU; also called intermodal transport units -ITU) like containers (ISO/maritime, ACTS, AWILOG etc.), swap-bodies and semitrailers.
In the intermodal transportation, three types of semitrailers are used -standard (non-cranable), intermodal (cranable) and bimodal. This paper is focused on systems related to road/rail transportation of standard and intermodal semitrailers. Bimodal semitrailers' transportation systems The application of Multiple-criteria decision making (MCDM) methods to identify the most suitable system is included (in section 4).
The paper is focused on segment of semitrailers because these days it seems to be the most promising. The share of semitrailers on the intermodal transportation market is continuously growing. According to UIRR Annual Report for the years 2019-2020 the share of semitrailers on intermodal transportation market (regarding transport volume) has been increasing since 2007 and currently is almost 15% (UIRR, 2020). Despite the "corona-crisis", the number of consignments transported in intermodal semitrailers has grown 4.89% in 2019. For trucking-companies the operation of standard semitrailers doesn't involve any further (higher) investments into their vehicle-fleet. As well as, higher usage of semitrailers' transportation systems will help to achieve target of moving 30% of current road cargo transport (with transport distance over 300 km) to rail and water transport until 2030 -as stated e.g. in Ministerstvo dopravy (2018) and CargoBeamer (2020a).

Literature review
The paper is Europe-oriented and it focuses exclusively on currently running systems. The scope of our research (literature review) corresponds with it. The analysed systems are: Modalohr, CargoBeamer, pocket wagons, NiKraSa and ISU. In sections 3.2 and 3.3, the details regarding these systems are presented. All hereinbefore mentioned systems will be considered as variants in the MCDM methods -see section 4.
Besides studying characteristics of individual semitrailer transportation systems, the researched area (European market) has been analysed from wider environmental point of view -particularly how freight transport negatively influence environment and what are the measures suitable to be taken to mitigate these impacts. Göçmen and Erol (2018) are solving environmental consequences of transport but even considering social factors (accidents and deaths) and risks associated with transportation of dangerous goods. In addition, the problem of non-cranable semitrailers' transportation by rail is often discussed. According to (van Leijen, 2020) and (Bíró, 2019) current share of intermodal semitrailers on European transport market is estimated to ca. 3-10%. In other words, 90-97% of all semitrailers are standard (non-cranable). This creates a huge potential for modal-shift from road to rail through implementation of intermodal transportation systems for standard semitrailers. Van Leijen (2020) describes a project for standard semitrailers with potential of moving 50,000 semitrailers on rail (on a route between Netherlands and Poland) in the next 2-3 years. The benefits of modal shift from road to rail in countries Austria, Germany, Liechtenstein and Switzerland is solved by UIC (2020). According to den Boer at al. (2011) it is estimated that maximum potential share of rail freight transport is in the range of 31-36% -i.e. the performance of rail transport can potentially double (compared to the current state).

The target of the paper and methods used
Besides the analysis of semitrailer transportation systems, the target of this paper is to apply MCDM methods WSA (Weighted Sum Approach) and TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) for the selection of the most appropriate system of transportation of semitrailers by railsee section 4. The authors have used two MCDM methods to verify the results. For determination of criteria weightings, the Fuller triangle method has been used. For details regarding chosen methods see section 2.5.

Research question and hypothesis
The paper answers the research question (RQ): "Which semitrailer transportation system to expand throughout Europe to support modal-shift from road to rail?" Hypothesis: based on the research, the authors expect the most suitable semitrailer transportation system to be one of the horizontal ones -either Modalohr or CargoBeamer.
The authors decided to use following criteria for evaluation of variants (systems of semitrailer transportation): 1. railway track (siding) electrification possibility, 2. need of investment into intermodal (cranable) semitrailer, 3. number of personnel needed for transhipment in a terminal, 4. the degree of risk of damage to the semitrailer during transhipment, 5. transhipment costs.
Considering hereinbefore specified criteria, it is clear the authors have chosen criteria relevant for "both sides" of intermodal transportation -i.e. the intermodal transportation operators (terminal operators respectively) and trucking companies.
The criterion number 1 has been included to consider possibility of railway track electrification in a terminal. In the case the transhipment is vertical, the electrification of railway track (siding) in a terminal is not possible. In the case the transhipment is horizontal, the electrification is possible. Criterion number 2 represents need of higher investments into intermodal semitrailers for trucking companies. Intermodal semitrailers are more expensive and heavier (ca. 300-500 kilograms) in comparison with standard ones. Criterion number 3 considers the impact on labour costs. The data used in this criterion are obtained from Klemenčič and Burg (2018). Criterion number 4 takes into account potential additional costs (resulting from damage to a semitrailer during transhipment) for trucking companies. In this criterion, the authors considered individual transhipment principles and evaluated the level of risk.
Criterion number 5 compares individual systems according to transhipment costs (in Euro, excl. VAT) as analysed by Klemenčič and Burg (2018).
The criteria matrix (also called decision matrix) is shown in Tab. 1. This matrix is the input into both methods considered -the WSA and the TOPSIS (see sections 4.1 and 4.2 respectively).
Tab. 1 The criteria matrix; source: Authors. The values in criterion "rail electrification possibility" have this meaning: if certain system requires vertical transhipment, it means the railway track (siding) can't be electrified -therefore value "zero" means electrification is not possible, value "1" means electrification is possible as the particular system belongs to horizontal ones.

Semitrailer
Only the first criterion has maximizing character (see the last line in Tab. 1), the values of other criteria will be converted to maximization (see further in section 4.1 Tab. 4 and 4.2 Tab. 10). The principle of conversion of minimization to maximization is described e.g. by Stopka et al. (2019).
The values in criterion "investment into cranable semitrailer" have the same meaning as the first criterion -i.e. "zero" in the case the trucking companies needn't invest into intermodal (cranable) semitrailer, and "1" in the case the trucking companies have to invest into intermodal semitrailer.
The values in criterion "number of personnel needed" are self-explaining.
The values in criterion "potential risk of damage to semitrailer" has been determined by authors according to the literature review and the study of characteristics of individual systems. The higher the value of the criterion is, the higher the risk of damage to the semitrailer is.
The values in criterion "transhipment costs" are self-explaining. The values represents the costs (in Euro, excl. VAT) of semitrailer transhipment in a terminal.
As already mentioned above, we will use the Fuller triangle method for determination of criteria weightings -see Fig. 1. The criteria which are more important compared to the others are highlighted with yellow colour and bold font. The application of Fuller triangle method is presented in Tab. 2.
Tab. 2 The preferences and weightings of criteria; source: Authors.

Number of preferences
Weightings of criteria From the results in Tab. 2, it is clear the criteria relevant for trucking companies have significantly higher weightings. This ensures the best suitable system of semitrailer transportation (identified by the MCDM methods) will be "user friendly" for trucking companies.
As the social target is to make modal-shift from road to rail, in the end the trucking companies will be the ones who will make final decision whether to drive door to door "on their own wheels" or whether they will use more ecological and safer intermodal transportation.

The selection of MCDM methods
The WSA method has been chosen due to the speed of determination of results -and is highly recommended by Stopka et al. (2014). The TOPSIS method (more sophisticated compared to the WSA) is widely used in MCDM problems (it is often mentioned and used in scientific papers) in logistics and transport -e.g. Bottani and Rizzi (2006) are using TOPSIS in the field of outsourcing of logistics services, Perçin, S. (2009) evaluates third party logistics providers, Li et al. (2011) are using TOPSIS for location of a logistics centre -similar to Stopka et al. (2014) who are solving allocation problems of logistics objects, presenting MCDM methods (e.g. ORESTE, TOPSIS, AHP and WSA) as well as methods for determining criteria weightings (e.g. method of ranking, Fuller triangle method and Scoring method). Velasquez and Hester (2013) states that areas of the TOPSIS method application are "supply chain management and logistics, design, engineering and manufacturing systems, business and marketing management, environmental management, human resources management, and water resources management".
The Fuller triangle method has been chosen because for the purpose of this paper, it is possible and sufficient to decide whether one criterion is more important than the other. It is not necessary to use -for instance -Saaty method which is using 9 point scale (Stopka et al., 2014).
Principle of the methods used will not be described here -only the application will be presented (see section 4). The theoretical background of the MCDM methods can be found e.g. in: Chýna et al. (2012) or Spackman et al. (2009).

Application of MCDM methods
The general procedure (sequence of steps) in the MCDM process is as follows: 1. identification of variants -in our case: the list of semitrailer transportation systems to be compared (the list of variants is above in section 2.4), 2. identification of criteria -in our case: relevant characteristics of systems considered (the list of criteria and their explanation is above in section 2.4), 3. determination of criteria weightings -in our case: the application of Fuller triangle method (the results are above in Tab. 2 in section 2.4), 4. application of specific MCDM method -in our case: application of the WSA and the TOPSIS method (see further in sections 4.1 and 4.2), 5. interpretation of results -identification of the most suitable variant and discussion (see further in the last paragraphs of sections 4.1 and 4.2, and the discussion in section 5).

SYSTEMS FOR TRANSPORTATION OF SEMITRAILERS
As mentioned hereinbefore, there are three types of semitrailers on intermodal transportation marketstandard semitrailers, intermodal semitrailers and bimodal semitrailers. Each of these types has specific construction defining possibilities of their manipulation (transloading techniques) in intermodal transportation terminals. The type of semitrailer regarding cargo it is designed to transport is irrelevanti.e. it doesn't matter whether the semitrailer is a platform vehicle (with canvas, curtainsider), box-body, refrigerated, tanker, silo etc. During rail transport, maximum permissible weight of loaded semitrailer slightly varies according to individual system (type of railway wagon respectively) -it can reach ca. 33-38 tons. Trains usually reach maximum speeds either 100 kmph or 120 kmph.

Transloading techniques
Generally, there are two principles of manipulation with semitrailers -horizontal and vertical. Horizontal systems are usually called Ro-Ro (Roll-on / Roll-off) and vertical systems called Lo-Lo (Lift-on / Lift Off).
In the case the Ro-Ro systems are used, it is possible to transload any type of semitrailer -this is, of course, beneficial. The Lo-Lo systems either require intermodal (cranable) semitrailers or usage of specially designed transhipment systems for standard semitrailers. These systems are solved hereinafter.

Modalohr (LorryRail)
Modalohr is a French system for transportation either semitrailers or semitrailer-combinations (including drivers travelling in a couchette wagon coupled in a train). It has been in operation since 2003. The system is universal in its use in unaccompanied and accompanied intermodal transportation. Primarily, it is operated in unaccompanied version.
Central part of Modalohr wagons (loading-deck) is rotary (ca. 45 degrees to the side). The turning process is done via electric motors mounted in the railway track in a terminal. A semitrailer is pulled on a wagon by a tractor (or terminal-tractor) and uncoupled from it. After this, the centre part of a wagon is turned back to the driving position.
The advantage is that each wagon is loaded individually, all the wagons in a train may be loaded simultaneously. The transloading time is very short -the whole train may be loaded with semitrailers in ca. 30-40 minutes (LOHR, 2016a), (LOHR, 2016b). The principle of transhipment in Modalohr system is shown in Fig. 2. On the line Barcelona -Bettembourg, it is estimated to save over 22,000 trucks/year on the road, representing a reduction in CO2 emissions of 23,070 tonnes/year (Todd, 2019).

CargoBeamer
The project originally started in 1998. The pilot project took place in Leipzig (D) -a terminal for three CargoBeamer wagons has been built. First tests of CargoBeamer system were on the route between Spain and Germany -semitrailers have been loaded with cargo for automotive industry (Volkswagen AG). Since 2015, the line between Kaldenkirchen (D) and Domodossola (I) has been in operation. Since opening, more than 70,000 semitrailers has been moved from road to rail (CargoBeamer, 2020b).
On May 14 th 2020, new line connecting Kaldenkirchen (D) and Sestokai (LT) has been opened. The target is to implement CargoBeamer system in its horizontal transhipment form (for explanation see the next paragraph). But if necessary (due to lack of special transloading equipment in a terminal), vertical transhipment of semitrailers is possible. The principle of standard semitrailers' transhipment is then the same as in the case of NiKraSa system (see further in section 3.3.2), or direct vertical transhipment of intermodal semitrailers takes place.
For horizontal transhipment of a semitrailer onto CargoBeamer wagon, the detachable central part (loading platform, also called a "pallet") of a wagon is positioned radially next to a wagon. On the platform a semitrailer is pulled by a tractor (or a terminal tractor) and dropped there. Then the platform is moved back onto a wagon. The loading process of the whole train takes 15-20 minutes (CargoBeamer, 2020c). The transhipment process in CargoBeamer is shown in Fig. 3. According to CargoBeamer (2020b), a new terminal is under construction in Calais (F). The terminal will be able to unload and load trains with up to 36 semitrailers, in a fully automated process within 20 minutes. The opening of the Calais terminal is scheduled for spring 2021. Routes from Calais to Great Britain (via Eurotunnel and ferries) are planned.
CargoBeamer system enables very quick transhipment of semitrailers between two trains, as well. This is beneficial primarily in terminals situated at the area where different rail-gauges meet (typically "normal" and "wide"). It is relevant at France-Spain border, Slovakia-Ukraine border etc. Complete transloading process between two trains takes ca. 1 hour, compared to 2-3 days "standard practice" when vertical transhipment is used (CargoBeamer, 2010). CargoBeamer system eliminates competitive disadvantage for rail transport compared with road transport.

Pocket wagons
System of pocket wagons is still the most important system in unaccompanied intermodal transportation. Pocket wagons are suitable for transportation of semitrailers, swap-bodies and ISO (maritime) containers -i.e. they are highly universal. Unfortunately, transloading of hereinbefore named ILUs is always vertical. In perspective of this paper, solving transportation of semitrailers, it is a disadvantage for trucking companies as they need to invest into specially designed intermodal (cranable) semitrailers.
Intermodal semitrailers are (in comparison with standard ones) more expensive and ca. 300-500 kilograms heavier -i.e. have lower payload. The other possibility is use of NiKraSa or ISU systems, developed for vertical transhipment of standard semitrailers (details are further in 3.3.2 and 3.3.3).
The transhipment of semitrailers onto wagons is usually done vertically by reach-stackers or gantry cranes (depends on size of a terminal and thus on its equipment). The principle of transhipment (using a gantry crane) is shown in Fig. 4. In the figure, the yellow rectangles on semitrailers are shown. On intermodal (cranable) semitrailers they mark places at which a gantry crane or a reach-stacker can grab the semitrailer and lift it.
Perner's Contacts 15(2), 2020 The necessity of vertical transloading brings a disadvantage related to railway traffic as well. The railway track (railway siding) can't be electrified. Transloading procedure in a terminal takes 2-3 hours, depending especially on the length of a train (number of ILUs transloaded) and on type and number of transloading equipment in a terminal.
The system enables vertical transhipment of standard (non-cranable) semitrailers using special platform -a type of trough, similar to the "pallet" used in CargoBeamer system (see section 3.2.2). The whole principle of NiKraSa system is similar to CargoBeamer system but with the difference that transloading of the platform with semitrailer is always vertical -see Fig. 5. The platform is positioned next to a train on terminal handling area by a reach-stacker or a gantry crane. Next, a semitrailer is pulled onto the platform using a tractor or a terminal-tractor. The last step is vertical transhipment of the platform with semitrailer into the railway wagon (Nagel-Group, n. NiKraSa system is using standard pocket wagons (e.g. type Sdggmrss) and it doesn't involve any additional investments into terminals infrastructure. The utilization of terminals can even be improved implementing NiKraSa system. On the other hand, positioning a semitrailer onto the platform brings potential risk of damage to the semitrailer (Cempírek, 2018).

ISU
The name comes from German "Innovativer Sattelauflieger Umschlag" -i.e. "Innovative semitrailer transhipment". History of the system goes back to the year 2006. The principle of ISU is based on special ramp which is placed in a terminal -and on which a semitrailer is towed by a tractor (or a terminaltractor). Then, a semitrailer is uncoupled from a tractor. Chain hinges (or textile-straps) are connected to semitrailer's king-pin (via traverse) and to 1 st and 3 rd axle (via wheel-grippers). Vertical transhipment into a wagon is then done via reach-stacker or gantry-crane (Hafner, 2019), (Possegger, 2012). Potential risk of damage to semitrailer structure (mainly to axle aggregate and tyres during lifting) is disadvantage of ISU system. Fig. 6 shows positioning of chain hinges at the semitrailer's kingpin and axles (on the left) and vertical transhipment into a railway wagon (on the right).

APPLICATION OF THE MCDM TO IDENTIFY THE MOST SUITABLE SEMITRAILER TRANSPORTATION SYSTEM
In this section we will present individual steps of the WSA and the TOPSIS methods and determine their results. The comparison of results of both methods and the discussion is presented further in section 5.

The WSA method
Individual matrixes, corresponding with individual steps, of the WSA method are presented in Tab. 3 to Tab. 8.

The TOPSIS method
Individual matrixes, corresponding with individual steps, of the TOPSIS method are presented in Tab. 9 to Tab. 16.
Tab. 9 The criterion matrix; source: Authors. The result: according to the TOPSIS method, the best suitable system is CargoBeamer. Its value of indicator of relative distance from basal variant is 1.00 (when considering three decimal numbers: 0.995).

FINDINGS AND DISCUSSION
The authors demonstrated application of MCDM methods on determination of the best suitable semitrailer transportation system in Europe. According to results of both the WSA method and the TOPSIS method, the best suitable system of semitrailer transportation is the CargoBeamer. The CargoBeamer belongs to horizontal transhipment systems -i.e. it is perfectly suitable for trucking companies operating standard (non-cranable) semitrailers. The vast majority of trucking companies operate this type of semitrailers. At best, only 10% of semitrailers are intermodal (cranable) -i.e. enable vertical transhipment in intermodal transportation terminals.
The Modalohr system is the second best according to both methods. It has reached 0.85 (in the WSA method) and 0.89 (in the TOPSIS method). Similar to CargoBeamer, the good rank is caused by the criteria weightings. The system NiKraSa has reached the third place -again in both methods: 0.65 in the WSA method and 0.58 in the TOPSIS method. The last two systems (ISU and pocket wagons) have different positions. According to the WSA method, the fourth place has the system of pocket wagons and the fifth place has the ISU system -according to the TOPSIS method, the rank is vice versa.
In general, the implementation of horizontal transhipment systems for semitrailers will have positive impact on modal-split. Currently, the share of road transport on European transportation market is 75.3%, the share of rail transport is only 18.7%. But, potentially, the rail transport could reach the share of 31-36% (den Boer at al., 2011). At least part of this increase could be due to (thanks to) higher performance of intermodal transportation.
In this paper, the authors have been primarily oriented on suitability of individual systems for trucking companies. If the authors would have chosen different criteria and/or counted different weightings of the same criteria, the results could be different. In the next survey, different criteria and their weightings can be used. We can primarily consider these cost-related criteria and technical criteria as: 1. the investment costs into terminals (regarding their location, size and particular system(s) operated), 2. the investment/lease costs into railway wagons designed for individual systems, 3. the capacities of trains used in individual systems (number of ILUs they can transport), 4. the degree of versatility of railway wagons used (regarding transportation possibilities of different types of ILUs).
By implementing hereinbefore mentioned criteria into MCDM methods we will increase the objectivity of choice of the best suitable semitrailer transportation system.