and expensive alterations to accommodate the new rolling stock that was poorly adapted for Line B. Due to the 6000 series cars using overhead lines for power collection, in contrast to the existing and functional third rail electrification system of Line B, a new solid overhead catenary system had to be installed. The new overhead power collection system turned out be insufficient in powering the 6000 series cars resulting in the cars operating at reduced performance leading to lower acceleration. The trains were significantly narrower than the Line B's original loading gauge necessitating the need for modifications to the trains to reduce the large platform gap. These alterations made the second-hand units not any cheaper than simply purchasing new rolling stock, as was done with the 200 Series on Line A. The rolling stock suburban interior design was a poor fit for the urban Line B. The seating was arranged as transverse seating, designed for long distance comfort with limited standing room which is a poor fit to Line B's typically short passenger trips with high passenger turnover at each station. The trains also were not completely walk through train sets as they were organised into married pairs. These factors and the narrow width of the train cars themselves led to very poor internal passenger circulation. The shorter cars meant that a 6000 series six car train made poor use of the existing platform length compared to older six car trains. These factors led to the new 6000 series rolling stock having a much smaller passenger capacity compared to the existing rolling stock. As of 2020, the remaining Eidan 300/400/500/900 sets are the oldest rapid transit cars that remain in operation in the world; the remaining cars are expected to be retired in the mid-2020s. Events and highlights When excavation was carried out for construction of the Leandro Alem station, the remains of a Mammoth of the Quaternary period where found, which were sent to the Museum of Natural Sciences of La Plata. Line B connects through a ramp at Federico Lacroze into the electrified track of the Urquiza Line, where the underground rolling stock heads to the Urquiza Railway workshops in Ruben Darío (Hurlingham) for wheel, gear and axle maintenance. Florida and Carlos Pellegrini stations are the two busiest stations on the line, as most commuters alight there in the morning to work in the downtown financial district. They