Adaptability of class I highway when reconstructed into expressway

In order to study the adaptability of reconstructing four-lane class I highway into four-lane expressway with the same design speed of 80 km·h^-1, operating speeds of typical road sections before and after the reconstruction were compared and analyzed based on field survey. The geometric alignment continuity and design consistency were analyzed. The mechanical properties were investigated before and after the reconstruction by using the triaxial accelerometer. At last, the IHSDM software of the latest version was used to predict the crashes and analyze the safety situation. The results show that the speeds of passenger cars are significantly increased after the reconstruction, especially on the non-geometry limited sections and downgrade sections. Moreover, the speeds of passenger cars are more sensitive to the geometric alignment change, which requires a balanced geometric alignment design. After reconstruction, the superelevation of sharp horizontal curve for passenger cars is deficient. Meanwhile, the vertical acceleration on the sharp vertical curve increases. Both of them reduce the comfort of riding. The safety analysis shows that the crash rate declines by 12.4%-20.32% after the reconstruction.