Reviewing Australian and New Zealand methods of correlating the radius, superelevation and friction in horizontal curve design

摘要

The paper reviews Australian and New Zealand methodologies of correlating the radius of horizontal curve (R), the superelevation rate (e), and the side friction (f_R), when the radius is above the minimum. The relationship between e and R was established by assuming a linear relationship between the superelevation rate and the radial friction coefficient. The proposed model, implements the radial utilization friction factor concept in order to generate the e(f_R) distribution coefficient (γ). When the model was applied to Austroads (2009) and New Zealand (2005) maximum superelevation policies and their recommended side friction factors, it resulted in an increase in horizontal curve radii as the superelevation approaches its minimum. The proposed methodology reserves smaller side friction values as the superelevation becomes smaller until e=e_(min) such that driving along the horizontal curve becomes safer and more comfortable for the driver. This reduces the pressure exerted on the steering wheel as the horizontal curve radius increases.