The City of Ottawa utilizes a Dynaflect to monitor the change in pavement strength during the spring thaw at 11 test sites selected to represent their arterial road network. As the average deflection of the sites approaches a threshold value, the load restrictions are imposed by way of signage and advertisement in the local newspapers. The restrictions remain in effect until the deflections again decrease below the threshold value. Enforcement is conducted by local police equipped with portable weigh scales. The goal is to allow for the shortest possible restriction period while ensuring that the road infrastructure is protected. However, the decision to implement the load restrictions is traditionally made too late, as prediction of the thaw progression between weekly deflection testing is difficult. As such, the City's pavements are occasionally subjected to full load hauling during the initial and most critical portion of the spring thaw. To better predict the onset and progression of the spring thaw in 2005, the Thaw Index (TI) was used in addition to deflection testing. An analysis was conducted as to whether the TI (as calibrated by the Minnesota Department of Transportation) would predict the same implementation date as suggested by City of Ottawa deflection data. Results of this analysis determined that the calibration factors provided by MinnDOT are sufficiently accurate in the Ottawa environment. Future investigation will involve the use of surface curvature index (SCI), as well as direct temperature measurements from the City's Road Weather Information Systems (RWIS).
Abstract