Salinity sensors have been traditionally employed in road weather information systems (RWIS), which focus on the pavement conditions (and meteorological conditions) of a small sample area (typically less than 0.1 sq. ft.) . The working mechanism of such in-pavement salinity sensors generally entails the measurement of brine conductance (passive approach) or freezing-point depression (active approach) . There are also portable instruments (such as SOBO-20) available. SOBO-20 sprays a measuring fluid (e.g., 85% water and 15% acetone) onto the enclosed pavement surface area and subsequently calculates the salt quantity based on the electrical conductivity of the collected fluid. More recently, there are non-invasive sensors that rely on algorithms to estimate the salt concentration on pavement .

Salinity sensors can be used to monitor the residual salt concentrations on the road surface, helping maintenance managers make educated decisions related to chemical reapplication and avoid over- application. If placed on a mobile platform (e.g., snowplow), these sensors monitor the salt concentration on pavement along entire stretches of roadways, which allows for more accurate chemical application rates. In other words, on-vehicle salinity sensors would be crucial components of mobile RWIS. A more advanced scenario would entail the integration of salinity sensor readings with automatic spreader controls to apply the right amount of chemicals in the right place. Note that integration was an underlying goal in several U.S. winter maintenance vehicle-based technology projects, including RoadView, Mn/DOT’s Advanced Snow Plow, and the Highway Maintenance Concept Vehicle. There is continued support in the winter maintenance community for similar vehicles that use integrated technologies to improve operations and safety, including: Automatic Vehicle Location (AVL), surface temperature sensors, freezing point and ice presence detection sensors, salinity sensors, snowplow blade position sensors and application rate sensors.

The first phase of this project included a literature review and practitioner survey.  This project encompasses the second phase, which includes development of a work plan for testing one or more salinity sensors, laboratory testing, field trials, and data analysis of the results.