Prague's metro system is, for many people, one of the jewels of the city, and it has fans all over the world. Its three lines (the green A line, the yellow B line and the red C line) are iconic, and they give the impression of being fixed. But what people may not know is that actually plans are in place for a fourth line, the blue-coloured D line. But why? Why does Prague need another metro line? To answer this question, Danny Bate spoke to Adam Scheinherr. Dr. Scheinherr is currently a councillor for the city of Prague, and was, from 2018 to 2023, the deputy mayor of transport. Since 2024, he has been the chairman of the local party Praha sobě (‘Prague for itself’).