Network for Transport Measures

6. Rail cargo transport

Methods and manuals > Wikis > 6. Rail cargo transport
Methods and manuals > Wikis > 6. Rail cargo transport

For environmental calculations for rail transport an investigation of the models and methods developed and used for energy and environmental calculations for travel and transportation by rail was initiated early in the project. For NTMCalc it is desirable to have a model in which the parameters with the greatest impact on the end result is included (at the same time as data for these parameters can be found for the presentation of the default values), but also for a situation-specific transport.

In summary, there are no readily applicable models that meet all the criteria set up by NTM, which are as follows: to calculate the energy use and emissions to air from the locomotives and power plants, not too complex but with variables corresponding to the key parameters that control the size of the train’s total running resistance (train’s own weight + weight of loaded cargo, train speed, number of start and stop, aerodynamic profile and parameters based on actual train operation), openly published reference from neutral player and covering a broad geographic area.

The literature study showed that the NTM criteria had not previously been addressed. The models that were found consisted of two main types

  1. High-resolution (scientific / research) methods based on the train physics and track design and traffic operation or
  2. Methods based on statistical data for a variety of trains (national statistics, operator statistics, etc.) estimated through the total energy/fuel consumption divided equally among the overall train traffic (ton kilometer or passenger kilometer).

For NTMCalc it is best to base the calculations on relational connection based on measurement data of real trains, preferably by taking into account the differences that exist between different train/cargo /car types, cargo volumes and traffic patterns. Unfortunately there is no high resolution operational statistics available internationally in this way which makes it difficult to create relevant modeling equations based on such different types of train, wagon types, railway operating modes, load type, single track or multiple tracks, etc.

The most comprehensive statistical database for train energy use was found at the UIC – the International Union of Railways (4). Unfortunately, the data in this database is confidential and thus not accessible. In the literature review, we found that another project (5) processed this database and created approximate relationship between train weight and the amount of electricity required for its propulsion. These correlations were therefore selected for use in NTMCalc 3.0 when they satisfied the following requirements; based on actual operating data, if not publicly available datasets, good geographical coverage, access to some default data for the filling degree and positioning distances.

The first calculation step is based on the weight of the wagons pulled by the locomotive followed by a correction factor in order to compensate for variations in topography (mountains, hilly or flat). Based on data for the total train weight loaded and empty, degree of filling of loaded trains and how long any extra empty position distance is (linked to the specific line haul) the entire energy consumption is calculated. If it’s a diesel locomotive that is used the total emissions from the locomotive are calculated.

For electric traction the size of the losses occurring in the transmission of electricity from power plants and locomotives are calculated, after which emissions for electricity generation are calculated. To get a proper connection between the locomotive’s electricity consumption and the type of electricity production NTM uses the production-specific calculation method. This means that it is the power generation technology selected by the train operator (or its agent) and contracted with by the electricity supplier is used as the basis for the calculation. Since electric power generation shows very large variations in performance, it is important that the correct information is used in the calculation. In the event the operator does not have the possibility to select specified supplies (or chose not to do so), the data for a national average mix is used. In some studies where it is not interesting to link the environmental impact of electricity to a specific consignment of goods, one can use NTM energy data combined with appropriately selected environmental data for marginal production, e.g. in scenario analysis when one wants to study the effect of increased or decreased transport by rail. For both diesel fuel and electric power generation, also the emissions resulting from the production of diesel fuel and the fuel used in power stations are calculated.