Passive and active roles

News Roads&Bridges December 08, 2003
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Should we send the salt trucks out tonight

Should we send the salt trucks out tonight? For those of us who are responsible for maintaining safe roads while minimizing costs, this question is one that we often ask.

Knowing what is happening at the pavement surface is essential to making the best decision. Today's most comprehensive pavement surface information is provided by a large number of Roadway Weather Information Systems (RWIS) and their embedded pavement sensors. The collected data enables users to make timely and informed decisions regarding road treatment timing and strategy. From a historical standpoint, the collected pavement data provides a solid base for optimizing future treatment programs.

The most important benefit of the pavement sensor is its ability to gather data remotely so it is not necessary to be everywhere during hazardous weather. A second benefit is to obtain non-visual information we cannot obtain by driving to the specific location, such as pavement temperature and the freeze point of water/chemical solution on the road.

Although several different sensors are available, all are based on one of two basic pavement sensor technologies: passive or active. The basic principles of the two technologies are very different. Passive sensors do not alter the state of the substance on the pavement. However, the active pavement sensor uses cooling and heating to alter the state of the material it is sensing. The following sections provide an introduction to each sensor technology and its value to our roads and bridges.

For more on the story, read the December issue of ROADS & BRIDGES magazine.

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