## 3 Results
### Energy and Power Requirements  
To evaluate power and energy requirements, a double traction 1300 t train (1 Hbis and 12 tank wagons, e.g., four-axle Zags 117 m\({}^{3}\) transporting liquified petroleum gas type 2 [51], and two locomotives 333.3, see Figure 3a) has been simulated in the example track. Another possibility in this route is a train with 12 intermodal-container wagons class Sgnss 60\({}^{\prime}\) to link Cartagena harbor, but the weight should be very close to Zags. The justification of this choice is based on the methodology used in some freight transport statistics [6] based on public European databases. According to these reports and the proposed methodology for  
Figure 14: Tractive effort of single units: (**a**) Series 333.3, 319.2, and 269.2; (**b**) Hybridization of 333.3 and 269.2 (rebuilt to a single-motor unit), 319.2, and 269.2 (single-motor) and Bombardier 3 kV DC TRAXX family (e.g., class S253 of RENFE in Spain). Figure 13: Simplified layout for locomotive subseries 269.6 according to Mitsubishi Electric specifications for Spanish manufacturers [50]. M1 and M2 (DC motors); 1 (3 kV rack for M1); 2 (chopper for M2); 3 (chopper for M1); 4 (3 kV rack for M2); 5 (filter); 6 (ancillary motor–generator group, 380 V); P1 and P2 (3 kV pantographs). data analysis, the average weight of goods loaded onto trains in Spain was 350 t with an average distance of 390 km in 2005 (and an average weight of around 500 t). Nevertheless, heavy trains could transport twice or threefold these numbers. Secondly, the admissible length of trains (according to the infrastructure operator, ADIF) is 320 m on this route. Third, the city of Cartagena has developed refining activities since the 50s, and most gas products are delivered by train. This justified the weight and class of wagons. Figure 15 shows the main results from our PBLM-Rail simulator in the Cartagena-Murcia itinerary. From Cartagena (CT) to El Regueron (ER), there are four stations with a secondary track to make a crossing possible. In the simulation, two stops have been considered because some passenger services would require these stops (this is a single-track section; see Figure 1a). Stop times are not very significant from the point of view of energy requirements, and three minutes are considered for simulation. The second stop is just before the train climbs the highest slope on the track (10-12%), which corresponds to the highest power requirements for locomotives. Results show that the freight train demands around 900 kWh, and braking accounts for 590 kWh (around 500 kWh go to braking resistors). Figure 15a,b clearly show that the main braking zone corresponds to the braking effort developed to maintain speed limitations when the train goes down the hill after the station RS; see the elevation profile, Figure 1a. The reader should also consider that Spain is a mountainous country (the second-highest country in Europe, surpassed only by Switzerland) and that conventional routes (1668 mm gauge) have important slopes and frequent curves that make haulage difficult but also benefit regenerative braking. Also, it is interesting to note that power demand does not require 4450 kW from the two 333.3 locomotives except when the train starts after the train stops and when the train climbs the hill in the route section from BS to RS stations. A cumulative demand/generation curve for this route (e.g., from CT to MC train stops) is depicted in Figure 16a. Cumulative load-duration curves (LDCs, as shown in Figure 16a) are commonly used by system operators in PPS to determine the utilization of generation resources. In our case, the analysis focuses on a small Power System (RPS) composed of two diesel-electric units. A preliminary examination of Figure 16a suggests that a single S333.3 unit could meet hauling requirements 85% of the time, including braking (albeit with reduced performance and increased reliance on pneumatic braking).