Chennai metropolitan area
The Greater Chennai Metropolitan Area, or simply the Chennai Metropolitan Area (CMA), is the fourth-most populous metropolitan area in India, the 22nd-most in Asia, and the 40th-most in the world. The CMA consists of the core city of Chennai, which is coterminous with the Chennai district, and its suburbs in Kanchipuram, Chengalpattu, and Thiruvallur districts. The Chennai Metropolitan Development Authority (CMDA) is the nodal agency that handles town planning and development within the metro area. Since 1974, an area encompassing 1,189 km around the city has been designated as the CMA and the CMDA  has been designated as the authority to plan the growth of the city and the area around it. Economy. Recent estimates of the economy of the Chennai Metropolitan Area is US$110 billion (over $200 billion with industrial zones)(PPP GDP), ranking it from third to fourth most productive metro area of India, and the third highest by GDP per capita. The metropolitan area doesn't include the nearby industrial zones of Siruseri and Sriperumbudur, due to which these regions' economy doesn't get included in the total economy of Chennai. If these regions are included, the economy of Chennai  would be somewhere over $200 billion. Composition. The CMA is a metropolitan area in Tamil Nadu state, consisting of the state capital Chennai (previously known as Madras) and its satellite towns. Developing over a period of about 20 years, it consists of 2 municipal corporations, 7 municipalities and 14 smaller town councils. The entire area is overseen by the Chennai Metropolitan Development Authority (CMDA), a Tamil Nadu State Government organisation in charge of town planning, development, transportation and housing in the region. The CMDA was formed to address the challenges in planning and development of integrated infrastructure for the  metropolitan region. The areas outside Greater Chennai Corporation (Chennai District) like Kanchipuram, Chengalpattu and Tiruvallur have lacked organised development. The CMA comprises the city of Chennai and its neighbourhood corporations of Avadi and Tambaram, 8 municipalities, 11 town panchayats and 179 village panchayats in 10 panchayat unions. The CMA has an area of 1,189 km. It includes the whole of the Chennai District, along with the Ambattur, Gummidipoondi, Madhavaram, Ponneri, Poonamallee and Tiruvallur taluks of the Tiruvallur District, Sriperumbudur and Kundrathur taluks of the Kancheepuram District, Pallavaram, Vandalur and Tambaram taluks of the Chengalpattu district. The CMA falls in three  Districts of the Tamil Nadu State viz. Chennai District, part of Thiruvallur District, part of Chengalpattu District and part of Kancheepuram District. The extent of the Chennai District (covered in Chennai Municipal Corporation area) is 426 km and comprises 55 revenue villages in 10 Taluks [viz. (i) Tondiarpet Taluk, (ii) Perambur Taluk, (iii) Purasawalkam Taluk, (iv) Egmore Taluk, (v) Mambalam Taluk, (vi) Guindy Taluk, (vii) Mylapore Taluk, (viii) Velachery Taluk, (ix) Aminjikarai Taluk and (x) Ayanavaram Taluk. In Thiruvallur District out of total district area of 3,427 km, 637 km in Ambattur, Thiruvallur, Ponneri and Poonamallee taluks fall into the  CMA. In Kancheepuram District out of 4,433 km, 376 km in Tambaram, Sriperumbudur and Chengalpattu district fall in the metropolitan area. CMA region has about 3,000 water bodies, most of which have been encroached upon by real estate dealers and small communities. The Chennai metropolitan area is set to be expanded further, incorporating the entire districts of Chengalpattu, Tiruvallur and Kancheepuram, and the Arakkonam taluk, Nemili Taluk of the Ranipet district. In future it may expand further. Plans to expand Chennai Metropolitan Area seven folds from existing 1,189 sq. km to 8,878 sq. km appears to be scaled down in  view of opposition from farmers in giving up their agricultural lands. The government is looking at maximum utilization of the available spaces in the core city and urbanized pockets in the suburbs for residential development. Only area well connected with the available rail infrastructure will be included in the expansion plan of CMA. The extent of expansion will be scaled down from 8,878 sq. km to 3,000–4,000 sq. km. Taluks. In Chennai district In Tiruvallur district In Kanchipuram district In Chengalpattu district Expansion. The CMDA regulates developments in the Chennai metropolitan area through the issuance of planning permission under section  49 of the Tamil Nadu Town and Country Planning Act 1971. The first plans to expand the CMA were proposed by the CMDA in 2011. The need for expansion arose as several nearby settlements such as Sriperumbudur, Kelambakkam, Tiruvallur and Maraimalai Nagar had been undergoing rapid development and had to be incorporated under the CMDA planning strategy. Also, the planning bodies of other metropolises in India such as Bengaluru, New Delhi and Hyderabad had already redefined their respective metropolitan regions to include much larger areas and corresponding regional planning was being done. The CMA, however, has not been altered since  it was first defined in 1974. The area was limited to which is among the smallest in the country. In July 2012, the CMDA suggested two options to the Government of Tamil Nadu for expanding the area: Chief planners of the CMDA have suggested that the second option is more feasible. Another planning model, similar to the National Capital Region was also examined by the CMDA. In order to plan for balanced regional development, developing a larger road network, implementing an integrated transport plan and identifying a Chennai Mega Region have become necessary. On 3 July 2017, the Government of  Tamil Nadu's minister for housing and urban development, Udumalai K. Radhakrishnan announced its intention to expand the CMA to . The extension will cover all of Kancheepuram and Tiruvallur districts and Arakkonam taluk of Ranipet district, as proposed in July 2012. Having completed a feasibility study, a "strategic regional plan" was now required, and completion of the whole process was expected by July 2018. On 22 January 2018 the Government of Tamil Nadu issued order G.O. (Ms) No.13 to "declare the intention to include additional areas in the Chennai Metropolitan Planning Area" under section 2, clause (23-a) of the  Tamil Nadu Town and Country Planning Act, 1971 (Tamil Nadu Act 35 of 1972). The additional areas to be included were as proposed by the CMDA in 2017. Under Tamil Nadu Act 35 the Tamil Nadu government is required to allow reasonable opportunity (two months according to §10.3) for inhabitants, local authorities and institutions in the area to comment upon or object to such an expansion proposals. Although less than 100 objections to the expansion plans were received, a public interest litigation action was launched at the Madras High Court in March 2018.