Table 3.

For each city, we compute the number of stations in the core (for the year 2009) and from the numerical calculation of N(r) we can estimate r_C the size of the core (in kilometres) from N(r = r_C) = N_C.

City	NC	rC (km)
Beijing	63	4.4
Tokyo	123	5.0
Seoul	243	11.6
Mexico	90	4.7
Shanghai	57	3.7
Moscow	39	5.9
London	142	7.3
Paris	186	4.2
Madrid	113	4.4
Berlin	68	5.5
Barcelona	57	3.5
Osaka	46	3.6