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  Road Weather Information System (RWIS) & Clarus

Road Weather Information System (RWIS) & Clarus



Clarus is not an acronym. Clarus means "clear" in Latin. The FHWA Clarus Initiative was a multi-year effort to develop and demonstrate an integrated surface transportation weather observation data management system, and to establish a partnership to create a Nationwide Surface Transportation Weather Observing and Forecasting System.

The Clarus System was designed to enable various public agencies to more accurately assess weather and pavement conditions as well as their impacts on operations. Such knowledge is critical for planning, conducting, and evaluating the effectiveness of activities such as winter road maintenance, weather-responsive traffic management, traveler information dissemination, safety management, transit vehicle dispatching, and flood control. The Federaly Highway Administration collaborated with NOAA to transition all Claurs functionality into MADIS.

The Road Weather Information System (RWIS) data is a combination of atmospheric and road observations. Atmospheric data include air temperature, humidity, visibility, wind information (speed and direction), precipitation information (type, rates, and accumulations), and cloud cover. Pavement data include road temperature, freezing point, condition (e.g., wet, icy, flooded), and subsurface conditions (e.g., soil temperature and moisture).

MADIS currently supports RWIS ESS sensor types and the MADIS team is continually adding new Clarus providers and enhancing current provider data and metadata.

Geographic Coverage

United States CONUS, Alaska, and Canada.

Data Schedule

Data schedule is set by provider and ranges from every 5 minutes to once per day. The current and previous hour's data are processed every 5 minutes. Data are stored based on their observational time stamp in netcdf files that contain observations from the top of the hour until 59 minutes into the hour (e.g., the 0000 file covers 0000 - 0059).

Data that arrive after 2 hours following the time of the observation are processed in a "data recovery" mode, where once a day batch processing is performed to reprocess data that are 35 days, 7 days, and 1 day old. These data are available with all communications methods supported by MADIS except for ldm.


Typical daily volume for all MADIS datasets can be seen here.


Please see the restrictions overview page for further information on RWIS location restrictions.

Variable Details

Last updated 27 June 2017