Effect of adverse weather conditions on speed-flow-occupancy relationships

The effect of adverse weather conditions on the flow-occupancy and speed-flow relationships is studied. The data used in the analysis were obtained from the Queen Elizabeth Way Mississauga freeway traffic management system. Regression analyses were performed to select proper models representing the flow-occupancy and speed-flow relationship for uncongested operation. Then dummy variable multiple regression analysis techniques were used to test for significant differences in traffic operations between different weather conditions. It is concluded that adverse weather conditions reduce the slope of flow-occupancy function and cause a downward shift in the speed-flow function. Adverse weather conditions also reduce the maximum observed flow rates.