Clarus Weather System


Much of the information that is used in weather models to develop forecasts is gathered by instruments sent aloft by weather balloons or by weather-sensing radar systems. These tools are effective in the management of air transportation, but are not sufficient in helping agencies to manage and operate the surface transportation system. Weather-related questions are typically asked by highway transportation agencies:

  • The radar shows rain, but is the rain reaching the ground?
  • The air temperature is just above freezing, but are the roads becoming icy because the ground is below freezing?
  • What are the actual surface conditions on our roads and bridges?
  • Do we need to warn the public of adverse weather conditions detected by our roadside weather sensors?


In the past, the data produced by road-weather information system (RWIS) networks have been consumed and analyzed by the individual state transportation departments owning those networks. Weather, however, doesn't begin or end at the border of a state; in fact, it completely ignores jurisdictional boundaries and lines drawn on maps. The Clarus Initiative is a Federal Highway Administration (FHWA) program that uses local and regional road and rail weather observations to enhance transportation operations across a broader community.

Cooperation between state departments of transportation—specifically, sharing environmental observation information—will lead to better decision making capabilities regarding the operations and maintenance of their respective roadways. The value of any single RWIS network is multiplied many times over when its information is combined with adjacent RWIS networks and distributed to a larger group of users.

The Clarus system is a perfect example of this type of RWIS network integration. The purpose of the Clarus system is to collect environmental information from heterogeneous sources, apply industry-accepted quality checking algorithms to that environmental information, and disseminate the environmental information along with the quality checking results to interested parties. Clarus exists precisely to facilitate the flow of high-quality environmental data among government agencies and other users.