1) Mumbai is already suffering from massive space constraints and traffic issues. A trip in a car is usually slower than walking that distance (assuming the infrastructure exists and you can walk without falling into an open pothole).
Mumbai desperately needs more public transport, and needs to add safe biking, also because of #2
2) Mumbai has very few roads per person, and further, it doesn’t have space to build anymore. Besides the fact that this means cars are not sustainable at all in the city, it also means there’s not too much quiet asphalt that would be needed to replace the existing road material.
3) Mumbai already has an excellent public transport infrastructure, especially with buses. That system is currently unworkable because of all the cars clogging the road. If you were to have dedicated bus lanes, and increase service drastically, it would solve most of Mumbai’s transit issues.
4) Cars in Mumbai rarely travel over 30km/h anyways. Just moving usa. Welcome miracle for the most part.