NEW DELHI: With the urban population set to double in the next 25 years, Union Minister of State for Urban Development Ajay Maken said on Friday that the much talked about Bus Rapid Transit (BRT) system is a must for all cities as it is their future. In case of Delhi, too, where the system has experienced a lot of teething troubles, 409 km of route has been envisaged at a cost of Rs.4,510 crore.