What city did actually function before the invention of individual motorized traffic? Rome? London? Would you want to live there back then as a simple citizen?
Is this a serious question? Let's take 1900 as an example year that's before individual motorized traffic (the car existed but clearly wasn't popularized). New York had a population of 3.5MM. London was 6.5MM. Paris 2.7MM.
If we're going to identify something key to the growth of cities, surely it is mass transit. Much of this isn't apparent in modern cities in the USA because so many of them tore apart their streetcar systems in the middle of the 20th century as policies shifted to favor the private automobile. But mass transit seems to me like the thing that drove the growth.
Well it wasn't full of diesel and petrol fumes. The great stink was forty years earlier, they already had decent sewage systems (many of which are still in place now).
If we're going to identify something key to the growth of cities, surely it is mass transit. Much of this isn't apparent in modern cities in the USA because so many of them tore apart their streetcar systems in the middle of the 20th century as policies shifted to favor the private automobile. But mass transit seems to me like the thing that drove the growth.