Abstract
Original scientific paper The turns from highways to settlement areas are achieved by link roads. For the safety of these turns, turning radii are required to be large. However, it is not always possible to achieve these turnings by means of arcs of circle with large radius, as different factors, such as topography, the state of settlement, problems impossible to overcome and economic conditions, do not allow designing such a route. Instead, for the sake of traffic, linear variation of the line curvature or maintaining the line curvature at constant value is highly desirable. One of the line geometries is the clothoid egg curve. Single and double type clothoid egg curves are used in many applications. In this study, the calculation and design of double-egg curve are explained by equations and figures in detail. For the design of two egg curves used in rotation from main road to connecting road in transportation networks as application, an example is provided for a better understanding of the subject. The main points of rotation geometry with the coordinates of auxiliary points and other intermediate results are given in a table. The main purpose of this study, the theory and calculations of two egg curves will provide basis to practitioners on a sample in a detailed way. By the fulfilment of design and its calculation of this rotation geometry which provides safer and more comfortable driving, it is hoped to be useful for practitioners.
Highlights
In transportation networks, two-way traffic between main roads and settlement units is attained by link roads
The purpose of this study is to demonstrate the calculation and design of double-egg curve by equations and figures in detail, especially for the applicability of the curve in the transportation networks
The application of double–egg curve has the ability to suit both topographic and economic conditions at the highest level. This is because a double-egg curve is composed of successive lining of seven different axes of pieces having different parameters
Summary
Two-way traffic between main roads and settlement units is attained by link roads. For the sake of safety, the turns in these link roads are required to be performed by means of circular curves with large radius. This is not always possible as different factors, such as topography, the state of settlement, problems impossible to overcome and economic conditions, do not allow designing such a route. Two of these pieces of axis are clothoid, three are arcs of circle and two are pieces of clothoid, i.e. egg curve The curvature of these segments changes linearly or partially keeps constant without sudden variations to minimize the effect of centrifugal forces (Fig. 1 a, b, c)
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