What leads to horizontal expansion of urbanised areas?
Cities typically see cost of land increasing in central areas due to concentration of economic activity and more people seeking space for housing and businesses. The natural response is to increase the allowed density so that people can create more floor space. However, in Indian cities, the densities are capped well below what the market would support. As a result, people have to look outward to find space for development. This results in horizontal expansion of urban area.