Fortunately you have answered yourself.There is a colleration between development and cars congestion.Countries with congestion like India,China,etc are among the developed.Why because that shows many people have ability to buy cars and to pay running costs for those cars.
Correlation is not synonymous to causation.
It is not because of many cars that they have development BUT because of development that they have many cars. Having many cars is a sick symptom of development just like obesity is a sick symptom of affluence (richness). If you are obese it doesn't mean you are healthy.
Some of the Benefits of having many cars are as follows:
1) Many spare parts shops will be opened (you really need Jesus)
2)many petrol stations will be opened (Ditto)
3)many car wash services will be opened (Ditto)
4)many garages will be opened (Ditto)
All these will have effects in the economy by increasing government revenue through taxes also will solve the problems of unemployent because many mechanics will be needed in garages,petrol stations,sparepart shops,car wash services etc
Congestion isn`t a big problem, it only increases fuel consumption per kilometer which means more tax to the government per kilometer for each litre of petrol consumed in the congestion.
Do you follow the world trends in global warming? I am not even sure I should engage you any further. There are some basic fundamentals you seem to be missing.