The line between Santos, the largest port in Southern America, and São Paulo is being operated by MRS Logistica and includes the 10.3 percent ramp between Raiz da Serra and Paranapiacaba. It is electrified with 3,000 V DC and has an Abt rack system. After some rack locomotives designed by Hitachi in the seventies, MRS received seven new locomotives which were delivered by Stadler from Switzerland in 2012. Now these carry the title of being the most powerful rack locomotives in the world.

They have an axle load of 30 tonnes and need a larger loading gauge than that of the rest of the line. Each locomotive has eight traction motors, four for the adhesion wheels and four for the cog wheels. Together these provide a power of 5,000 kW and a starting tractive effort of 760 kN or around 170,000 pounds. The cabs are mounted relatively high to provide better view over the train that is being pushed uphill.

The company operates seven of these locomotives which are being designated He 4/4 by Stadler, since this would be their type designation in Switzerland. Due to the high price, these locomotives are being dubbed “Rolex” by the employees of MRS Logistica. Usually two locomotives are working together, what allows for train weights of up to 850 tonnes. After the rack section, diesel locomotives are taking over the trains.