There isn’t really a “good idea” alternative to packing people around the same area; higher density is dramatically more cost-efficient for providing the same quality of public services and infrastructure and the same kinds of employment opportunities.
The question then becomes: if n people are going to live in the metro area, where someone in any nearby housing might plausibly work at any nearby job, what is the most convenient and effective way of organizing the space? The answer is: put a high density of housing and jobs directly next to transit corridors, so that many people can find work within a reasonable commute from their house (or can find housing within a reasonable commute from their jobs) without creating traffic bottlenecks. If instead you follow the LA model where density is mostly uniformly low, and commuting is via low-bandwidth freeways, then what you end up with is people living 2 hours from downtown and leaving home at 4 AM every day to beat the traffic, and other people stuck crawling down the highway twice a day.
* The denser the area, the slower the transportation (by any mean).
* People in dense areas spend more time commuting than people in sparse areas.
* When you upgrade the infrastructure making transportation faster, people move farther, keeping their commuting time constant.
It's just that packing people around the same area is not a very good idea, whichever way you do it; there is no true solution to the problems it causes.