NS invested €618 million in 2017 (€791 million in 2016), mainly in trains for implementation of the HSL solution, New Generation Intercity trains, New Generation Sprinter trains, Stadler FLIRT trains, the overhaul and modernisation of the VIRM-1 trains and changes to the maintenance centres to enable the maintenance of the new rolling stock. NS made joint investments with ProRail in the Amsterdam Centraal, Utrecht Centraal and Den Haag HS stations, among others. Investments were also made in IT systems for managing rolling stock and staff, and in customer service systems such as the journey planner, which is aimed at improving the door-to-door journey for passengers.