Field Tests on Lateral Operational Characteristics of Passenger Cars on Helical Ramps (Bridges)

Helical ramps and helical bridges are widely used in recent years, however the driving patterns and dynamic characteristics of vehicles running on them are still unclear. Therefore, to obtain the driving pattern of passenger cars on helical ramps (bridge), driving tests using real cars were carried out on Fuling Yangtze River Bridge, Second Fuling Wujiang River Bridge, Rongqiao Helical Bridge and Jinkai Helical Bridge in Chongqing. Trajectory and lateral acceleration speed of cars under drivers’ naturalistic driving were continuously collected, as well as environment information. Based on naturalistic driving data, the variation, amplitude and influencing factors of speed and lateral acceleration were obtained, together with lane usage pattern. It was found that diversified lateral acceleration patterns on helical ramps were observed, such as stabilized, increasing, deceasing, and drum-typed. Larger lateral acceleration were recorded on ramps along the inner ring than on ramps along the outer ring. Lateral acceleration measured on some one-way ramps are significantly higher than the recommended valve in highway design guidelines and even exceeding the unbearable threshold, which cause passengers discomfort in side direction. Ramp radius and driving space greatly affect lateral acceleration, lateral acceleration drops as ramp radius increases if driving space holds constant, and the smallest lateral acceleration was measured on mixed two-way helical ramp. For one-way helical ramps with two lanes, regardless of on upward ramp or downward ramp, driving on inside lane accounted for a major proportion of driving patterns.