Methodological approaches evolution to container trains design with differentiated length

. The current limitations of sustainable growth of railway container traffic at the present stage are analysed. The article analyses the main organisational and technological parameters of container trains on the Russian railway network and the requirements for their implementation. It is revealed that strict compliance with the requirements to form a container train of unified length of 71 conventional wagons does not always meet the requirements of commodity owners and does not improve the conditions of supply of their products. On the other hand, in the conditions of a deficit of throughput capacities of the railway infrastructure in some directions, there is a need to increase the length of container trains up to 114-140 conventional wagons. Within the framework of the development of methodological approaches to the establishment of expedient organisational and technological requirements for the assignment of container trains, a classifier of solutions for sorting of container trains of differentiated lengths based on the technical and economic characteristics of a particular railway direction has been developed. The application of the original classifier will increase the validity of the organisation of container trains of differentiated length, taking into account the growth of commercial attractiveness of the transport service for goods owners and economic efficiency for the railway carrier and the organisers of container trains.


Introduction
The Transport Strategy of the Russian Federation for the period until 2030 singles out the increase in the level of cargo containerisation as one of the key areas of transport complex development [1].Containerisation is one of the key elements in the development of the logistics direction of JSC "Russian Railways".The Russian container market demonstrates stable growth: over the 10 years from 2011 to 2021, the volume of transportations on the railway network increased by 143.8%, which is demonstrated in Figure 1.
blue -domestic green -export grey -import yellow -transit Fig. 1.Container transportations on the railway network of JSC "RZD for the period from 2011 to 2021.
In 2022, due to a fundamental change in the direction of foreign trade in the country, there were serious changes in the logistics of commodity flows, and the balance of transport volumes between countries changed significantly [2][3][4][5][6]: friendly countries saw an increase of 23% to 365 million tonnes; the volume of countries that imposed economic sanctions fell by 37% to 210 million tonnes.A historically maximum volume of 275.6 million tonnes (+3.3% against 2021 and +4.0%above 2019) was achieved within the boundaries of the Eastern polygon railways.
Despite increased sanctions pressure, the withdrawal of the world's largest container operators from the Russian market, the disruption of established logistics chains and the need to reorient transportations gravitating to the ports of the North-West to the ports of the Far East and land border crossings, container transportations on the JSC "RZD" network grew by 0.3% in 2022.
At the same time, it should be noted that the degree of cargo containerisation in Russia is much lower than in the world practice (Fig. 2).The reasons for this are both subjective and objective.The Russian economy is mainly focused on the supply of raw materials to the world market, while exports of finished products, which are subject to containerisation, account for a small part.Containers come to the Russian market mainly with import cargo.The containerisation rate in this transport segment is 34%.The Russian railway container transport market accounts for only 6.9 % of the total freight traffic.Fig.The radical restructuring of cargo flow logistics, the departure of the world's largest container operators from the Russian transport market have led not only to an increase in the load of transport and logistics infrastructure of the Eastern polygon, but also to a significant increase in the time of containers and specialised rolling stock in transit and, consequently, their turnover time, which, in turn, caused an increase in the required working fleet of containers and specialised rolling stock [7][8][9].
As of spring 2022, the deficit of the container fleet was estimated at 250-300 thousand TEU, which was about a third of the working fleet.Due to the support measures implemented by the state, the forecast of the deficit level was reduced to 77 thousand TEU.
In order to reduce the duration of containers' stay at terminals and eliminate the deficit of the fleet of specialised fitting platforms, container loading into gondola cars released from under coal is currently used.This allows the use of rolling stock, which was previously sent empty.However, gondola cars are not specialised for container transportation.Loading containers in them is associated with longer loading and unloading operations, the need to use special inserts when securing the container in the gondola, and increased complexity of ensuring the safety of cargo during transport.

Materials and methods
In the current conditions and in order to achieve sustainable growth of container transportations, to improve the long-term competitiveness of JSC "RZD in the freight transportation market and the quality of transport services to goods owners, it is necessary to implement organisational and technological solutions that provide a systematic increase in the efficiency of the process of cargo transportation in containers for all its participants.
Compared to various variants of rail transport of containers, transporting them by container trains has an obvious marketing advantage: they are not only faster, but also cheaper compared to other ways of sending containers.In essence, a container train (CT) is a dispatch route from the sorting station to the destination station without re-forming, consisting of fitting platforms loaded with loaded or empty containers.A fundamental organisational and technological requirement regulated by JSC "RZD" is the provision of guaranteed infrastructure resources in the form of firm schedule strings (development of an agreed schedule) under the CT of permanent sorting.At the same time, in accordance with JSC "RZD" regulations, a container train must travel at least 550 km per day, but the average route speed is usually higher by more than 2 times.CT movement according to the schedule has affected the determination of delivery times for cargoes transported by means of CT: only the time the train is in transit -from the departure station to the destination station -is taken into account.CT length range established by JSC "RZD" is from 57 to 71 conventional wagons.The main organisational and technological parameters of CT and the requirements implementing them are presented in Table 1.  1, it is obvious that the dominant factors of successful promotion of such transport product on the market of transport and logistics services as regular CT are relatively high route speed for the majority of transportations and timeliness of cargo delivery.
However, it should be remembered that one of the main requirements of cargo owners remains minimisation of cargo transportation costs.At the same time, the costs of shippers or the CT organiser tend to be minimised only in case of timely dispatch of containerised products, which in a number of cases is not performed due to long periods of accumulation of containers up to the established length of goods trains on the Russian Railways network of 71 conventional wagons.
In addition, on the directions with low-intensity container traffic, strict compliance with the technological parameter of CT length requires the CT organiser to increase the frequency of CT dispatch, which, in turn, affects the increase in operating costs of goods owners associated with the storage of inventories, and the decrease in the railway carrier's profit due to the switching of container-accessible products to other modes of transport.
On the directions with high intensity of container flows in conditions of deficit of railway infrastructure capacity there is a need to increase the length of container trains up to 114-140 conventional wagons.
Thus, in order to establish optimal material and time costs in all elements of the logistics chain, it is necessary in the organisational and technological requirements for CT assignment to provide for the possibility of forming CTs of differentiated length, including those exceeding the established range.To improve the validity of decisions on the feasibility of assigning CT of differentiated length, a methodology has been developed that allows to solve the optimisation problems of choosing the length and frequency of running CT on a given railway direction, taking into account the parameters of demand for transportation, tariff, the number of cars in the container train, the number of locomotives used to transport containers, the time of delivery of container cargo, infrastructure constraints [10].In turn, to ensure the "transparency" of the order of CT organisation, a classifier of decisions on the assignment of CT of differentiated length is proposed.It is presented in Table 2.
Here under the "delivery time" is taken the time of promotion of container-accessible products from cargo owners or CT organisers to consignees, including the time of accumulation of container-accessible products for the sorting of CT of the set length.
The frequency of CT services does not change.
Increase in profits by attracting additional demand for rail transport due to tariff reductions.

Not available Deficit
The length of the train is determined from the declared transport volumes by the CT organiser ( dif
Container trains do not change their frequency. Fixing
There is no change in CT frequency.
Profit growth due to attraction of additional volumes due to tariff optimisation

Not available Deficit
Train length is determined from the declared transport volumes by the CT organiser ).
There is no change in CT frequency. Fixing
There is no change in CT frequency.
Fixing the current level of carrier's profit due to regular dispatch of container trains Thus, by applying the expedient organisational and technological requirements for CT sorting, specified in Table 2, in terms of its length, it is possible to organise a regular container service on a particular railway direction, ensuring the growth of commercial attractiveness of the transport service for goods owners and its economic efficiency for the railway carrier and CT organisers.

Results
Let us consider the definition of expedient organisational and technological requirements on the example of a CT running on the St. Petersburg -Novorossiysk direction.At present, 3 CTs with a unified length of 71 conventional wagons run monthly on this direction.The available capacity reserve allows for the monthly dispatch of 2 additional CTs.At departure of CT with minimum length, providing full repayment of demand declared by the organiser of CT, growth of demand for transportation will make 15%, and possible increase of tariff taking into account cost of transportation of containers on the considered direction by road transport makes 10%.
According to the parameters presented in Table 2, the demand is unstable, there is a reserve of throughput capacity, also Available Deficit of working fleet of containers and rolling stock.Based on these characteristics, it is advisable to revise the length of the CT train.
According to the results of calculations in accordance with the methodology presented in [10] the optimal variant is the dispatch of CT with the length of 56 conventional wagons.In this case, the turnover of containers and rolling stock relative to the initial organisational and technological characteristics will be reduced by 2.8 days, and the delivery time will be reduced from 17.1 days to 14.3.Profit will increase by 2352203,86 roubles per year.In turn, the cost of transporting 1 TEU will increase by 1639.86 roubles for the consignor, which is 586 roubles per day of delivery time reduction.
The annual demand for the carriage of containers in the direction under consideration, based on the value of the unified length of CT in 71 conventional wagons and the number of CT sent for the year, is 2,556 conventional wagons.
The required working fleet of containers for the organisation of CT traffic is determined as the product of the number of containers to be transported per day by the average turnover of one container.Under the existing organisational and technological requirements, it will amount to 122 containers.
In the case of the organisation of CT on expedient organisational-technological requirements, taking into account the increase of annual demand for transportation up to 2,767 containers and reduction of term of delivery on 2.8 days, the working park of containers will be reduced to 110 containers.At the same time, the required working fleet of containers in the direction under consideration will be reduced by 12 units, and the number of requests for the carriage of goods handled by a container of the working fleet will increase by 19%.

Conclusion
Thus, the development of methodological approaches to the establishment of organisational and technological requirements for CT assignment, including the use of the original classifier of solutions for the CT sorting of differentiated length depending on the technical and economic characteristics of a particular railway direction, will ensure sustainable growth of railway container traffic, as well as improve the long-term competitiveness of JSC "RZD in the freight market and the quality of transport services to goods owners.

Table 1 .
Main organisational and technological parameters of container trains on the Russian railway network

Table 2 .
Classifier of solutions for assigning CT differentiated lengths