Vermont’s National Highway System Analysis Map

Increasingly, GIS is a contributor to the decision-making process at the Vermont Agency of Transportation (VTrans). The technology can be used to quickly show areas of interest accompanied with different types of data. In the past, this would have involved producing large reports requiring reams of paper and time to comprehend. Maps of this nature enable designers to present the information needed in an easy-to-use format and aid in justifying certain actions and their financial commitments.

Average Daily Vehicular and Truck Traffic

The following hierarchy of analysis was used to develop annual average daily traffic (AADT) volumes: (1) an actual count, if one was available for the particular road segment; (2) an estimated volume based on actual count taken in a neighboring section used in conjunction with the appropriate turning movement traffic volumes; (3) an estimated volume based on applying the growth rate from a nearby count station to the AADT; and (4) if no counts were taken in the vicinity, applying the statewide average growth rate for the appropriate class of road to the AADT.

Roadway Sufficiency Rating

The present method for determining roadway sufficiency rating consists of assigning a point rating (structural condition, 50 points; safety, 25 points; and service, 25 points) to the various highway elements based on the actual condition, dimensions, and service of the highway and its ability or inability to carry the traffic efficiently when compared to a uniform set of standards.

Pavement Condition Rating

Automated surveys are conducted annually to determine pavement conditions across the state. Each segment of road is rated on a scale of 0 to 100 based on rutting, cracking, and roughness. The VTrans goal for this performance measure is 70.

High-Crash Locations

For a section or intersection to be identified as a high-crash location, two criteria must be satisfied: (1) the location must have experienced five or more crashes in a five-year period, or the average of one crash per year, and (2) the actual/critical ratio must be 1:000 or higher.

Structurally Deficient Bridges

Information about structurally deficient bridges is obtained by running the federal edit program, which can include any of the following criteria: the rating of the deck, superstructure, substructure, or culvert and retaining walls; structural condition; or waterway adequacy.