Research on Defining the Geometry Index for Safe Driving at the Curving and Sloping Sections for Freeway

In this paper, advanced devices such as the dynamic GPS and dynamic electrocardiogram equipment have been employed to monitor the car speed and the driver's heart rate in carefully designed driving tests. Thirteen selected drivers took the tests by driving the standard cars recurrently through the same highway testing section, which has the speed limit of 80 km/h and a length of 60km. The enormous data extracted from the testing results have been summarized and analyzed in this paper. Based on the correlation analysis, it can be concluded that the heart rate increment of the driver strongly correlates with the combination index of the curving and sloping section. On the other hand, no apparent correlation can be identified between the driving speed and the heart rate increment. By applying the linear regression analysis, a quantitative model has been established for the longitudinal gradient, the radius of the horizontal curve, and the heart rate increment. The model has been applied to retrieve the safety threshold values for the geometric design of the curving and sloping sections at a specified speed limit. The research result of the paper will provide the useful theoretical reference for revising the Design Specification for Highway Alignment.