Abstract: The purpose of this study is to quantitatively analyze the dangerous sections of the reserve continuous curves with small radius for two-lane mountain highway. To achieve this goal, field tests were done in a reverse continuous curve of Fuzhou Forest Park to Guling highway taken as the research object. In the tests, a portable laser-based traffic survey instrument was applied to investigate traffic flow parameters, and the video recording method was used to collect the magnitude of travel trajectory offset. Subsequently, based on measured data and calibration value of section point, a three-dimensional model was built for describing relationships among the travel trajectory offset, location of observation point and driving velocity. Finally, lengths and areas of dangerous sections for the continuous curve at different velocities were calculated based on three-dimensional model. The results indicate that when vehicle speed is greater than the critical value, there is a quadratic polynomial relationship between the velocity and the length or the area of dangerous section -- an increase in the velocity makes both dangerous sections range and dangerous level increase. According to the actual situations faced with the dangerous sections, the velocity limit for curve should be 20-27 km/h.

Key words: two-lane, mountain highway, continuous curves, travel trajectory offset, dangerous sections