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This paper presents an in-depth investigation of the engineering aspects related to the design and operation of distributed-power freight trains (F-EMU, freight Electric Multiple Unit), and their potential advantages, by evaluating the various components of this new kind of train and comparing its performance with a traditional freight train. Electric motors, distributed along certain motorised carriages of connected wagons, allow, among others, the power necessary to avoid multiple locomotives, used on traditional lines for the heaviest trains, to be supplied, and access to high-speed lines, which were originally designed and constructed – in Italy for example – for mixed use (i.e. for passengers and freight). Interesting speed levels (140160 km/h) could be achieved, subject to the other requirements of the rolling stock, which are indicated later on in the paper. EMU trains are known to be used for passenger services, as they allow high speeds to be reached, energy to be recuperated during braking and, in general, increases in the performances of the rolling stock to be obtained. Analyses of the operation of freight trains have pointed out that distributed-power trains are able to reach appreciable acceleration values, during traction, because of a better distribution of the adhesive weight. High performances can be achieved, during the braking phase, when electro-dynamic braking, which allows energy to be recovered, is adopted together with a dominant electro-pneumatic braking system: this also prevents the infrastructure operator from having to lengthen the block sections to allow any poorly-braking 700-750 m long traditional trains to transit. The use of such innovative freight trains also satisfies the modern requirements of intermodal transport: electrification of the whole train makes it possible to transport units of refrigerated goods and perishable goods, and to conduct a constant monitoring of the load. After having examined the design and functional requirements of the F-EMU train and a traditional one, a comparison is made of the performances of a distributedpower freight train and a conventional one, on the TurinSavona railway line, through the use of a micro-simulating software package that is able to reproduce the railway operations along the considered stretch and saturate the current passenger timetable with freight trains. From the results, it has emerged that the adoption of distributed-power freight trains leads to a marked reduction of the travel times and an increase in the intermodal transport units (UTI) that can be transported over the reference time frame, especially when considering the use of 750 m long trains. [ABSTRACT FROM AUTHOR]

The so-called heavy freight trains (over 1600 t), sometimes even long (740-750 m), are now among the leaders of the future of rail transport of goods. The aim of this paper is to analyse, both theoretically and experimentally, the impact that this solution may have on the traction units (hooks with their traction castle or yoke) and the braking system. Concerning the traction units, the technical reference in Italy, no longer binding from 2021, is Tab. 20, art. 61, of the General Preface of the Timetable of Services (named PGOS) containing the correlations between the maximum towed mass and the plan-altimetric characteristics of the line (performance grade). This reference is questioned and compared with other foreign institutional sources and with analytical calculations referring to “quasistatic” conditions of the trainset, departing from a standstill, and again in “dynamic” conditions at high speeds. As far as the analysis in the braking phase is concerned, this was carried out by means of thermal evaluations on data collected from experimental observations compared with data available in the literature. Among the main results, considering a precautionary limit hook load of 400 kN, both in the quasi-static and dynamic conditions, it appears that the maximum load section or degree of performance on which a train of 2000 t can circulate is 15/16, corresponding approximately to an equivalent resistance deriving from the infrastructure (i.e. gradient and resistance in curves) of 15‰, without prejudice to the possibility of using thrust or booster locomotives at the rear, in compliance with the provisions of art. 60 of the mentioned PGOS. The thermal evaluations of the braking system confirmed that the maximum values reached are compatible with those in the literature and that the behaviour of the braking blocks is different according to their type. [ABSTRACT FROM AUTHOR]