This paper demonstrates that strict adherence to the Transit New Zealand draft State Highway Geometric Design Manual geometric standards can lead to excessively long spiral transition curves that can convey misleading information to the driver. This paper presents a discussion on the influences that the rate of superelevation development and adopted lateral coefficients of friction can have on determining the length of a spiral transition from a tangent to a circular arc. A maximum length of spiral transition is suggested and the necessary corresponding adjustments to the rate of superelevation development are given. The focus of this paper is on rural two-lane highways with winding alignments and near minimum curve radii measured in relation to the speed environment and design speed. (Author/publisher) For the covering entry of this conference, please see ITRD abstract no. E215377.
Samenvatting