A couple of weeks ago, I suggested that cities give developers incentives to build dense, connected, local street networks rather than simply mandate them. After thinking a bit harder about it, though, I'm not sure that's the best solution.
Cities should refuse to maintain subdivision streets that do not provide a minimal level of connectivity for other city residents (as Virginia will now do). But should a city or state go one step further and mandate connectivity? Should it pay developers to provide connectivity? Or should it do nothing, other than leave the maintenance costs on subdivisions with functionally private streets?
Using incentive payments is sound in theory. Connectivity provides a spillover benefit to residents outside the subdivision because it lowers congestion on major arteries, gives them more alternatives for getting around, and solves a collective action problem. If bans on mixed-use development were also relaxed, connectivity could also shorten net trip length. (Connectivity alone won't do the trick.) The disconnected, cul-de-sac pattern is less expensive than a dense street grid. But if a city offered developers incentives equal to the value of connectivity to the city, then developers would build dense, connected grids when it made economic sense to do so.
There are a couple of practical problems with this, though. One is that no city could afford to do it, at least not for enough subdivisions to make a difference. The second is that it would be hard for the city to figure out what to pay. A city could pay for all subdivision streets. But see objection no. 1 (and cities shouldn't be subsidizing subdivision streets anyway). A city, in theory, should pay only for the extra street length needed to get up to a minimal level of connectivity. But that depends on what the developer would have built in the first place, and the city wouldn't be able to determine that.
That leaves regulation (mandating connectivity) or doing nothing.
Simply mandating connectivity eliminates the drain on the city fisc. It is more feasible, politically, than simply dumping money on developers, as Virginia has demonstrated. Regulation is a tricky thing, though. The cost-benefit analysis does not change merely because the city is no longer paying its share. And, again, connectivity can be very expensive.
Perhaps the best solution is a hybrid approach. Cities could mandate a certain minimal level of connectivity but let developers buy their way out of it. That might provide enough of a nudge to solve the collective action problem without mandating street designs that cost more than they are worth.
