The underground system can transport more passengers throught the city, quickly and safe, than any other means of transport.
It takes up very little space and does not need much energy in relation to its performance. And it is seen to be a driver of innovation in cities, because it connects different parts of the city and people in terms of their expertise.
This is why underground networks around the world are being expanded and modernised on an ongoing basis.
Building an underground system is expensive, however, and must take into consideration the other means of transport and the overall development of the city.
This makes planning an underground line a lengthy and complex undertaking – one that will be presented here.