In a generally interesting post, Mary Newsom includes a fascinating piece of information:

An intriguing study from Charlotte’s city staff illustrates another of sprawl’s hidden costs, with city taxpayers in this instance footing the bill: Fire station costs are sharply lower in older parts of town where streets connect. The study analyzed eight stations and found the annualized per-household life-cycle cost almost five times greater in disconnected, cul-de-sac-laden suburbia. That’s because fire stations in neighborhoods with traditional street grids can serve more square miles, since they can reach more homes within acceptable response times.

I grew up in the Raleigh suburbs, on a cul-de-sac, and the attraction of the design was obvious. Any given day, you could find a bunch of kids playing in the circle, because it was a central gathering place and traffic rarely came by. On the subdivisions central through street, however, there was a constant stream of traffic, and we were encouraged to steer clear by our parents. The main through street was quite busy, of course, because it connected the handful of ways to get in and out of the subdivision. Meanwhile, in a nearby development in which my family had previously lived, the residents agreed to cut off the through street, which connected two larger arteries, effectively cul-de-sacing the whole subdivision (and adding about a mile to the commutes of most of the subdivision’s residents). The reason, of course, was that the through street was one of the few routes between the two arteries in the area, and it therefore was subject to heavy through traffic. Most of the surrounding subdivisions had initially been built not to connect the two arteries, for just this reason.

The logic behind cul-de-sacs is easy to understand. Roads in suburbs, unlike roads in cities, are for personal automobiles and personal automobiles only — there is no sense of a mode sharing role for the streets. As such, neighborhoods feel the need to carve out special streets for playing. But when a development does this, is redirects more traffic elsewhere. This encourages developments elsewhere to cut off their through routes, too. Eventually, the result is an extremely broken street grid that adds time and miles to all trips — the ordinary and the emergency. At the same time, it encourages the mental division of streets into play street and driving streets, such that on driving streets, awareness of pedestrians and cyclists is diminished.

A complete grid is good for the city as a whole, but there is every incentive for each subdivision to be the one that deviates and cuts off their through streets. When everyone does that, however, everyone suffers. Cities need to make street connections a priority.

Of course to do that while satisfying homeowners’ desires for safe streets would also require a reconsideration of street design and planning. Room must be made, along the street and in drivers’ minds, for pedestrians and cyclists, and on residential streets, speed cannot be planners’ top priority.