Effect of Curve Length on Operating Speed on Horizontal Curve of Multilane Divided Rural Roadway

This study deals with evaluating and developing speed predictive models of vehicles on horizontal curves for multilane rural highways. A total of 37 sites were identified, and data were collected through field surveys in sections of Northern Iraq. Speed data were collected using a radar speed gun, while the curve length was measured using appropriate surveying equipment. The models were developed using Minitab 21 software and the simple linear regression method. Two predictive models were developed to estimate the speeds of passenger cars and heavy vehicles at the midpoint of the curve. The developed models indicate a positive correlation between vehicle speed and curve length. The coefficient for passenger cars (0.207) is nearly twice that of heavy vehicles, suggesting a more significant impact of curve length on the operating speeds of passenger cars compared to heavy vehicles. The authors suggested studying the effect of other factors on operating speed. In addition, they proposed developing models for each type of vehicle for different types of roadways.