The AURORA program has undertaken a study of the accuracy of various types of road surface temperature sensors in order to determine which classes and types of sensors offer the greatest accuracy.
AURORA obtained the cooperation of eight sensor vendors, who provided a total of nine different sensor models.
In order to accurately determine the actual road surface temperatures, a series of thermistors was installed in each test section. Reading for thermistors surrounding each tested sensor were averaged to determine a “true” temperature.
Two different types of sensors were studied. Fixed passive sensors are the traditional road weather information system component used to measure pavement surface temperature. These devices are installed in the pavement and use thermistors to measure the surface temperature. Data are then relayed to a data logger via either wire or radio transmissions. A second type of sensor in common use is the infrared radiometer. These sensors are usually mounted on a winter maintenance vehicle and measure the long wave radiation emitted by the pavement in order to calculate a pavement surface temperature.
Two sets of tests were run. The first was conducted in a laboratory environment. Various conditions were simulated. Solar flux was simulated. Various temperature ranges were examined, with both fixed and variable temperatures. Sensors were tested with and without the presence of the typical road de-icing agents. In addition, infrared sensors were tested at varying heights and were tested to determine acclimatization time.
The second set of tests is ongoing. Sensors are being tested under actual field conditions, with as many tests as possible mirroring the laboratory tests. This will be dependent on winter weather conditions at the test facility near Minneapolis, Minnesota.
Final results of the study will be available in Summer 2004.
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