A high proportion of roads built within the last sixty years, particularly in suburban settings, have been deliberately designed to minimize public utility and maximize individual privacy. Take the standard cul-de-sac that serves a handful of households. The purpose of this design is to exclude the general public from passing through while serving the automotive needs of a small number of individuals. Does it pass our intuitive sense of fairness to declare that the entire public, say the local municipal citizenry, ought to foot the bill for what could essentially be considered a shared driveway? Perhaps a more important question: How does the government's decision of where to draw the line between public and private encourage or discourage the connectivity of the road system?
Many of these roads within subdivisions are currently funded with a mixture of private and public monies. Typically, the developer pays for the initial construction and the state (in Virginia's case) covers the maintenance costs. However, VDOT is considering shifting the balance away from paying for semi-private roadways at all. In technical terms, they want to require a minimum link-to-node ratio in order to fund the maintenance of any road.
"The link-node ratio is calculated by dividing the number of links (street segments and stub streets) by the number of nodes (intersections or cul-de-sacs). A perfect grid of streets will have a link-node ratio around 2.5 and a network of complete cul-de-sac or dead end streets with only one way in and one way out will have a link-node ratio of 1.0. It is suggested that a ratio of 1.4 will provide adequate connectivity in many situations."
Connectivity is valuable. A well-connected street grid provides multiple routes to a given place. The denser the street network, the shorter the average trip length. A dense network relieves congestion by diffusing trips across alternate routes. A denser network of streets allows denser development and offers a better pedestrian experience.
The trouble with connectivity is that we get the benefit of a dense street grid merely by living near the grid; we don't have to live on the grid itself to enjoy the shorter trips or the reduced congestion. For many, the ideal would be a quiet cul-de-sac jutting off a dense street network. But if we try to satisfy this preference, things quickly degenerate into a game of "beggar thy neighbor" -- "Traffic for thee, but not for me." Neighborhoods fight to close off their streets or divert traffic, pushing more traffic through other neighborhoods, who then start their own campain, etc. In equilibrium, you get . . . Austin, where many neighborhoods have only one way to get from here to there.
Politically, disconnectivity is impossible to fix once it's been built into the network. The solution is to get it right up front.
But developers argue it is not not worth it. Street grids reduce the number of lots they can squeeze out of their subdivisions. Plus, they say, homeowners will gladly accept extra congestion and longer trips for quieter, child-friendly streets.
Subdivision developers already pay to build new subdivision streets. But they -- and their homeowner-customers -- know that once the roads have been dedicated, their maintenance is the city's responsibility. Pricing disconnectivity would get the incentives right. The city would assume responsibility for maintaining new streets only when the streets provided a "public good" -- i.e., a positive spillover to the street network. The developer would remain free to choose whether to plug in to the grid -- but he (or his customers) would be stuck with the cost of maintaining streets that did not extend the grid. We'd at least keep new developments from freeloading off the existing grid.
