No abstract

Advances in road weather sensing technologies have made non-invasive road weather sensors a valuable component in many Intelligent Transportation Systems (ITS) applications. The current study presents an investigation into the reliability of using one of the aforementioned sensors for a proposed weather-responsive variable speed limit system. The Vaisala surface state and temperature sensors (DSC-111 and DST-111) were selected for the proposed application. The sensors' ability to provide accurate and reliable data was tested under various conditions in a controlled laboratory environment. Specifically, four outputs of interest from the sensors were tested in this investigation; surface state, snow and ice depth, water depth and grip level. Testing results showed that the sensors determined the surface state (dry, moist, wet, snowy and icy) accurately and reliably. The sensor's snow depth readings were found to be inaccurate, while the sensor's ice depth measurements were found to be relatively close to the actual depths. In regards to water depth, only a limited number of readings were close to the actual depths while other readings were highly inaccurate. In an effort to test the potential of the sensor in providing reliable inputs to the proposed ITS application, a calibration was conducted for the sensor water depth measurements using various water depths and sensor installation angles. Calibration results showed that the water depth could be accurately estimated using the calibrated sensor measurements regardless of water depth or sensor installation angle. Sensor estimates of grip level were found highly correlated to the coefficient of static friction for the conditions considered in this study.

Winter highway maintenance activities offer direct and indirect benefits to the public. However, the cost of such activities is such a major outlay that it demands close scrutiny. There is a need to understand better and quantitatively estimate the benefits of winter road maintenance. Therefore, the work discussed in this paper was undertaken to quantitatively assess the benefits of winter highway operations at the state level. Methodologies were developed to estimate the major benefits of winter maintenance, including safety improvements, travel time savings, and fuel savings. A Minnesota case was used to demonstrate the methodologies and quantify those benefits. Results of the case study showed the benefits of winter highway maintenance by the Minnesota Department of Transportation to be $227 million per winter season, with $168 million of safety benefits, $11 million of mobility benefits, and $48 million of fuel savings. The benefit–cost ratio of winter highway operations in Minnesota was 6.2, in which material costs were taken into account.