VDOT to require more road connectivity

Virginia Department of Transportation (VDOT) is putting some finishing touches on a new Secondary Streets Acceptance Requirements policy, which would supplant Subdivision Street Requirements approved in 2005. The goal of this new policy is very clear. For the first time, VDOT will require “that streets accepted into the state system for perpetual public maintenance provide commensurate public benefit.” Although the plan includes many components, the element perhaps most likely to result in sweeping changes is a measured commitment to connectivity for all new road networks. In order to be accepted for maintenance funds, a proposed street network will have to look more like a grid and less like a series of cul-de-sacs.

The trouble with a disconnected road system, as VDOT sees it, is that local traffic is often funneled into major arterial roads, leading to congestion and all of the associated social costs. A connected system that allows multiple routes to a destination enhances travel efficiency, provides better response times for emergency vehicles, gives more options for detours, and reduces overall congestion. The Commonwealth Transportation Board (CTB), who authorized the drafting of the regulation, also pointed out that an interconnected street network could encourage pedestrians and bicyclists by providing options for travel away from crowded and dangerous transportation corridors.

Illustrations from policy summary provided to the Commonwealth Transportation Board (CTB)

To understand exactly what level of connectivity VDOT is aiming for, an obscure technical term needs to be introduced into the discussion: a link-to-node ratio. A node is an intersection or dead-end and a link is any segment of street between nodes. The higher the link to node ratio, the more connected a network of streets is. It frames the backbone of VDOTs new requirements by providing a quantifiable standard to be applied across the board during review of preliminary site plans. However, exceptions will be allowed for extenuating circumstances, and the regulations do include an appeal process to resolve differences in opinion between developers and government officials.

The required link-to-node ratio will very depending on which of three area types the network falls into. “Compact areas,” which include the City of Charlottesville and Designated Growth Areas of Albemarle County, will require a 1.6 score or higher. “Suburban areas” are within a two mile buffer of the Designated Growth Areas. They will require a 1.4 score or higher. Street networks in “Rural areas” outside of the suburban ring will not have a specific requirement but will need to show some external connections.

The Secondary Street policy was open for public comment from its initiation in 2007 until the summer of 2008, and a few suggestions were incorporated into the plan. It was pointed out that internal connectivity within the network would not provide the same benefit that connectivity outside the network would provide. The language of the policy was revised accordingly, to ensure that streets would bridge existing developments and remain open for new development.

Secondly, the public comments helped fine-tune the exception clause, which had been left fairly vague. In general, a developer would be able to automatically reduce the connectivity requirements by the proportion of the development bordered by a constraint. A constraint could be a river, a railroad track, anything that prohibits roadway access. This will provide a potential for streamlining the straight-forward cases, but some more complex proposals will still have to be reviewed on a case-by-case basis.

There have been some concerns expressed by citizens that these new requirements could compromise the privacy and safety of residential neighborhoods. Road networks could no longer be designed to block through-traffic. VDOT is meeting these concerns with a few other changes. Their traditionally wide street requirements will be narrowed considerably. Previous subdivision roads were required to have a width between 36 and 40 feet, a size that is known to encourage speeds in excess of posted limits. New streets will only need widths of 24 to 29 feet, unless on-street parking is a factor. This change is only possible, according to VDOT, because of the enhanced access for emergency vehicles connectivity allows. Transportation officials also recommend that the traffic impacts be mitigated through other traffic calming design strategies.

The change in Secondary Street Acceptance Requirements is expected to take effect in the beginning of 2009. There will be a 6-month transition period, within which developers can choose whether to submit a proposal under the new policy or the older one.

Specific Requirements by Area Type :

Compact Area

    Includes all of the City of Charlottesville and Albemarle County’s Designated Growth Areas

    Link-to-node ratio of 1.6 or higher (closer to a grid)

    A specific number of external connections, as determined by size of network

    Sidewalks along both sides of the street

Suburban Area

    2 mile buffer around Designated Growth Areas

    Link-to-node ratio of 1.4 or higher

    A specific number of external connections, as determined by size of network

    Sidewalks along both sides of the street or a system of trails and sidewalks, with exceptions for large-lot subdivisions.

Rural Area

    All other areas

    A specific number of external connections, as determined by size of network

    Trail system or sidewalk along one side of the street, with exceptions for very low-volume roads