<Dd> Category I--New tracks specially constructed for high speeds, allowing a maximum running speed of at least 250 km / h (155 mph). </Dd> <Dd> Category II--Existing tracks specially upgraded for high speeds, allowing a maximum running speed of at least 200 km / h (124 mph). </Dd> <Dd> Category III--Existing tracks specially upgraded for high speeds, allowing a maximum running speed of at least 200 km / h (124 mph), but with some sections having a lower allowable speed (for example due to topographic constraints, or passage through urban areas). </Dd> <P> A third definition of high - speed and very high - speed rail (Demiridis & Pyrgidis 2012) requires simultaneous fulfilment of the following two conditions: </P>

Which is the highest speed train in world