No longer will our children grow up hearing about Tokyo, New York and London being the biggest cities in the world. They will now hear of Delhi, Mumbai Beijing and Shanghai being among the biggest cities. Delhi is projected to overtake Tokyo and become the most populous city in the world. By 2030, it will have nearly 40 million residents and by 2050, this will go up to nearly 60 million.The question that arises is, how will such large cities be managed? More specifically, how will municipal services be delivered? The cities haven’t done a particularly good job in providing services to those at the lower end of the economic pyramid — as evidenced by mountains of solid waste, severe congestion, worsening air pollution and the terrible living conditions in large slums.How will cities serve mammoth populations like 40 million and 60 million? Will one municipality be able to serve so many people or should they be broken up into more manageable sizes?Experience from around the world is varied. While the Paris region, with about 12 million people, has 1,281 municipalities, Beijing, with a population of about 20 million, is a single municipality. Which is better? Smaller jurisdictions allow easier management of several local services but do not permit the economies of scale necessary for other services. Besides, larger jurisdictions facilitate economic interdependence over a larger area, including a larger labour market and more diversified access to jobs. The key seems to be in finding an optimal trade-off between economic interdependence and easier delivery of municipal services.As an example, some services like household waste collection are better managed in small municipalities, but disposal may need scale economies that require larger jurisdictions. Similarly, primary schools could be better managed in smaller cities, but universities will get a larger student body if they have a bigger captive population of students. Public bus services may be good for smaller populations, but high-cost mass transit systems are more effective to cater to larger populations.As the urban population grows, economic interdependence takes place across larger areas. For example, a lot of people work in Delhi, but travel from Gurgaon or Noida, and vice versa. Many work in Mumbai but travel from such far-off places as Pune. Such a trend will grow, largely due to the availability of reasonably priced housing and other quality-of-life issues. How do we deal with such situations? China is considering city clusters as expanded jurisdictions that have a much larger and economically inter-dependent population. While municipalities, with already powerful mayors, will continue to provide most services, cluster-level planning will be centred on rapid mobility solutions. Nineteen clusters are being planned, out of which three are already underway — the Pearl River Delta centred on Hong Kong, the Yangtze River Delta centred on Shanghai and Jingjinji around Beijing.If India were to think of a city-cluster approach, like in China, there would be a need to think of yet another level of government — beyond municipalities and metropolitan authorities. Perhaps a larger regional entity, something like a citycluster, will be needed. There would also be a need to classify municipal services into those delivered at the municipal level, metropolitan level and cluster level. Planning could follow a cascaded approach, with regional plans guiding metropolitan plans and these, in turn, guiding municipal plans. For example, an expanded National Capital Region, which also encompasses more distant cities such as Meerut, Panipat, Alwar and Rohtak, would become a national capital cluster. A regional rapid rail system is already being planned to connect this region and facilitate economic interdependence of a much larger area than the NCR. Smaller entities like the NDMC and the municipal corporations in Delhi could continue to offer other municipal services that do not require such a large captive population. Airports and universities could also be planned around such a regional approach. A sound governance mechanism will, of course, have to emerge.(The writer is a former civil servant and CEO of World Resources Institute-India)