BACKGROUND
At least 42 state departments of transportation (DOTs) and other public and private-sector agencies use road weather information systems (RWISs) to support highway-operations and maintenance decision making, public information messages, and weather forecasts by the meteorological community. These agencies typically specify requirements for the accuracy of RWIS atmospheric and pavement surface and subsurface sensor measurements at the time of procurement. Subsequent to the procurement, most agencies rely on vendor-developed testing and calibration methods or accept the sensor data without verification or regular and timely recalibration. However, uncertainty in the data generated by the sensors may compromise the value of this information. Guidance is needed for practical testing and calibration methods for RWIS sensors to ensure that the sensor is providing an accurate representation of actual conditions at the installed site.
Methods for atmospheric sensors applicable to RWISs can be derived from existing literature and practice. Further research is needed to develop testing and calibration methods for RWIS pavement surface and subsurface sensors. The results of this latter research can then be combined with existing methods for atmospheric sensors to provide practical guidelines for field testing and calibrating RWIS sensors.
Aurora, a consortium of several United States and Canadian DOTs and the Swedish National Road Administration formed to promote RWIS research and implementation, has investigated the state of the practice for testing and calibrating RWIS pavement surface and subsurface sensors. Their December 1999 report (see Special Note A) indicates that a number of countries and organizations were developing methods and standards for testing and calibrating RWIS sensors. As of 1999, only the Ministère de l'Equipment des Transports et du Logement of France had adopted and implemented guidelines for RWIS testing and calibration.
OBJECTIVE
The objective of this research is to develop practical guidelines for testing and calibration methods for reliable operation of RWIS sensors in field deployments. Methods for RWIS atmospheric sensors are expected to be available in existing literature and practice; therefore, the substance of this research effort will be the development and testing of methods for RWIS pavement surface and subsurface sensors. These methods should have the potential to be incorporated in performance standards and be used for data quality assurance. (The guidelines shall be produced using dual units, U.S. customary units and metric [S.I.]. The primary measurement will reflect prevailing practice in the subject area.)
Accomplishment of the project objective(s) will require at least the following tasks.
TASKS (1.) Review previous work in the development of testing and calibration methods for RWIS and similar sensing systems. This review should include, at a minimum, domestic and international literature, and surveys and interviews of RWIS users and manufacturers. This task should build on the state-of-practice report issued by Aurora and on atmospheric sensor testing and calibration methods and standards developed by the meteorological community. (2.) Draft an initial matrix of testing and calibration methods for various RWIS surface and subsurface sensors for, but not limited to, pavement temperature, surface state (e.g., dry, wet, frozen, and depth of snow and ice), chemical concentration or freezing point, and subsurface temperature and moisture. This matrix of testing and calibration methods for each sensor type should include a range of factors, such as accuracy, complexity, and cost of implementation. (3.) Develop and validate (at the bench-scale level) a field test plan for evaluating the most promising testing and calibration methods for surface and subsurface sensors from the matrix of Task 2. Working cooperatively with several state DOTs across varied climatic regions and pavement types and with an array of sensor technologies is highly encouraged. The field test plan should be sufficiently adaptable that lessons learned during the field phase of the investigation can be implemented immediately. (4.) Prepare an interim report on the information developed in Tasks 1 through 3. The interim report shall also contain the field test plan for testing and calibrating surface and subsurface sensors under Task 5. (5.) Implement the approved field test plan. (6.) At the close of the field test, identify those RWIS sensor testing and calibration methods that proved most promising for operational implementation. Prepare concise guidelines of best practices for RWIS sensor testing and calibration methods that can be distributed as a stand-alone document for use by RWIS end-user organizations. These guidelines should include both the surface and subsurface sensor test and calibration methods developed under this investigation and those methods found in practice for typical RWIS atmospheric sensors for, but not limited to, air temperature, atmospheric pressure, relative humidity, wind speed and direction, precipitation, visibility, and solar radiation. These guidelines for RWIS sensor testing and calibration methods will be provided to the NCHRP project panel for review. Panel review comments on the guidelines will be addressed in preparing the final report. (7.) Prepare the final report, including the details of Tasks 1 through 6. The final report should archive the field-test phase of the investigation, including lessons learned and modifications made to the sensor testing and calibration methods during the field trials. The final report shall include the stand-alone guidelines of best practices for RWIS sensor testing and calibration methods from Task 6.
Status: Completed
Product Availability: NCHRP Web-Only Document 87 is available online.
