to link the three major railway terminals of the city. Modernisation of existing lines Much of the modernisation in recent years has centred around the Underground's rolling stock, with large scale renewals and refurbishments of existing fleets, in particular on Lines A and H. Along with this came the construction of new underground workshops and storage areas on lines A, H and E, as well as the expansion of the existing facilities on Lines B and D. In September 2015, the president of SBASE highlighted plans for the 2015–2019 period for the Underground at a conference with other South American mass transit operators in Brazil. One of the largest changes to be made during this period was the upgrading of signalling systems on all lines, with the exception of Line E. Lines A and B were to receive Automatic Train Operation systems, replacing their ATS and ATP systems respectively, whilst lines C, D and H were to receive Communications Based Train Control systems. The implementation of these systems was already under way on Lines C and H as of September 2015, and was due to be completed on other lines before 2019. Line D was also to receive platform screen doors along with the CBTC system. Other works to be carried out during this period include the improvement of disabled access in older stations, new ventilation systems on lines B, C and D, improvements in electrification (such as replacing overhead lines and substations) on lines A, B, C and D and the replacement of 14 km of track on Lines C and E. The total investment in this period for these new projects was set at US$1.34 billion. Stations Starting in 2007, the network's stations began to receive technological updates ranging from Wi-Fi to interactive terminals. Through BA-WIFI (the citywide free internet service), passengers can use internet free of charge across all stations and aboard trains, though this has been delayed on Line A due to complications surrounding the line's age. There are also several "digital spaces" across the network and in its commercial galleries where seating areas are provided, along with recharging stations for mobile devices. There has also been widespread cosmetic changes to stations, including the restoration of historical murals, the incorporation of new artwork and improving the lighting. The renovations on Line B have been met with criticism for destroying parts of the line's historic heritage, which