Facilitating traffic - attraction or circulation

Picture any civic center, downtown, and urban district you've ever visited, and you'll see the same elements: a density of activity, a mix of uses, and a walkable street network. And on the periphery, some large parking lots and a major arterial. Self-contained autarky is impossible; local density alone cannot supply the dollars to support the commercial services or supply the staff for the commercial retail/services--any center must draw on people from outside the center and must facilitated people traveling to do so. But any center must also facilitate circulation within itself*, and it is that tension between attraction and facilitation that makes urban traffic such a muddle**. 

That tension can be resolved in favor of either, but results in very different outcomes. If attraction is subsidized, you get a very good network of higher speed roads between pods of development. If circulation is subsidized, you get a very high-quality pedestrian realm, comfortable local traffic, but very poor access for traveling long distances. Neither resolution is reliably superior to the other, but rather which should be preferred is context dependent.

 

*Also what makes freeway interchanges so hostile to urbanism and incapable of being 'centers': an interchange of an expressway with an arterial generates four islands of highly accessible land, equal in dignity, but prohibits circulation between them. 

** Grade separation resolves the urban traffic muddle but is expensive to implement. The contrived solution is grade separation--witness endless Chamber of Commerce plans for skybridges and pedways, and highway megaprojects like Boston's Big Dig, or Los Angeles triple-track rail trench. It's not a new solution--practically as soon as railroads emerged, demands for grade separation followed, generating elevated and subway lines.