Abstract
In China, the maximum design speed of highways is 120 km/h, which first appeared in the Highway Engineering Technical Standard (Trial) in 1951. However, vehicle performance, road design, and construction technology have been greatly improved over the past 68 years. To adapt to the development demands of highway design speeds above 120 km/h in the future, it is urgent to study superhighway alignment design theory. Therefore, the horizontal alignment security design theory of superhighways was developed in this paper. First, the definition, classification, and construction mode of a superhighway and suitable vehicles of different grades are presented. Then, the lengths of straight lines were limited to reduce driving fatigue. Next, the minimum radii of circular curves were calculated based on driver characteristics and stress analysis of operating vehicles. Finally, the minimum lengths of transition curves were calculated based on the centrifugal acceleration of the operating vehicles, the travel time, and the passenger visual characteristics. The calculation and analysis results show that the superhighway linear features conform to the vehicle operating characteristics, and can ensure the safety of driving.
Highlights
Superhighways are highways with a design speed higher than 120 km/h
The minimum lengths of transition curves were calculated based on the centrifugal acceleration of the operating vehicles, the travel time, and the passenger visual characteristics
After returning to China, I began to investigate the origin of highways expressway speed limit, and found that it first appeared in the design code published in 1951 with surprise
Summary
Superhighways are highways with a design speed higher than 120 km/h. Superhighways are different from ordinary highways. Research related to highway design speeds higher than 120 km/h is still mostly lacking in China [7], and there are very few studies from foreign countries [8]. Their study explored the relationships between alternative measures of horizontal alignment design consistency and the expected number of roadway departure crashes along horizontal curves on rural, two-lane, two-way roads. Such findings are intuitive given the concept of design consistency and represent advancement of existing predictive methods in the AASHTO (American Association of State Highway and Transportation Officials) Highway Safety Manual, which estimate the expected number of crashes on a segment as a function of the characteristics of only that segment.
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