A Layout Method of Guide Signs for Inner and Outer Lanes Integrated Composite Expressway

The integrated composite expressway has a special road structure and traffic organization mode, which requires the transmission of a large amount of information. In order to enhance the efficiency of guide signs, prevent information overload, and improve safety, research is conducted to optimize the layout of guide signs for this type of expressway. Using the Guangshen expressway as a case study, the research analyzes its characteristics of the inner and outer lanes to clarify layout principles for guide signs. It proposes information guidance methods based on the functions of inner and outer lanes and develops a grading method for guidance information. Through driving simulation technology, experiments are carried out to determine information threshold and layout design for guide signs. Drivers'target search time for different information quantities of guide signs is measured, as well as the lateral offset, speed, acceleration, and sign fixation time during interchange exits. In the information threshold experiment, robust estimation theory is applied to process the target information search time, concluding that the information threshold for guide signs on an integrated composite expressway is 8. In the layout design experiment, two sets of interchange exit guide signs are tested based on the proposed information guidance and grading methods. Both sets can correctly guide vehicles to their destinations. However, the guidance method based on the inner and outer functions proves more efficiency, leading to an earlier lane changes about 250 m, a 5.88% increase in driving speed, a 45.77% reduction in acceleration standard deviation, and a shortened sign fixation time. The research indicates that the proposed information guidance method effectively enhances sign visibility, guides traffic flow, and alleviates driver stress on integrated composite expressways. It is recommended to adopt the information guidance method based on the inner and outer functions for integrated composite expressways.