\r\nDB says it has already achieved a considerable amount during the last three years in what it describes as its largest network and station modernisation programme. More than 5000km of track have been renewed and 5500 switches renovated, while more than half of its 15,700 operationally-critical switches have been fitted with sensors. In addition, 8% of stations have undergone a refresh.\r\nDB will continue to tackle its investment backlog this year, and plans to renovate another 1600km of track, 1700 switches, and almost 2500 signalling installations. DB will also invest \u20ac1.2bn in station modernisation.\r\nWork is underway on 42 large projects, with another 12 scheduled to start soon, and a further 19 more planned to launch this year. In all, DB says it will have around 800 construction sites across the network in operation each day.\r\nWhile the scale of the work underway means the introduction of temporary speed restrictions, train diversions, and in some cases replacement bus services, DB says it is doing a lot to mitigate the effect on passengers. DB set up a special unit last year to optimise work sites to minimise delays to passengers, and says that despite there being more work sites in 2017 than in 2016, it managed to reduce delays to passengers by 10% last year.\r\nMajor station projects are underway in Munich, Dortmund and Hamburg, and DB will start work on modernising 700 stations this year. It says 77% of its 5400 stations now have step-free access, and it is making around 100 stations per year step-free.\r\nInfrastructure manager, DB Network, says it increased the number of construction workers by 770 to 17,700 and took on more than 500 apprentices last year, and it plans to recruit another 1500 employees and 580 apprentices this year.\r\nNext year, DB plans to begin upgrading its oldest high-speed lines, which are now nearly 30 years old, starting with the Hannover - W\u00fcrzburg line. This will be implemented in phases but will mean train diversions and cancellations. DB is also working on timetables to upgrade the Mannheim - Stuttgart and Hannover - Berlin high-speed lines.\r\n\r\nMajor worksite corridors in Germany in 2018.