# TOWARDS A NEW APPROACH FOR THE DESIGN OF THE ALIGNMENT OF HIGHWAYS AND RAILROADS

In this paper, a new curve is formulated to join two straight lines with a single element. Considering the use of curves in both horizontal and vertical geometry of a single route nowadays, it becomes clear that at least three different types of curves are utilized, i.e., circular, spiral and parabolic curves, while a single horizontal curve can consist of up to three separate elements. The form and geometry of the proposed curve is described in terms of the curvature at every position along the curve. It is demonstrated that this curve can be used when designing both the horizontal and vertical geometry of a route. Applying the proposed new curve, given the increasing design speeds, will ensure that vehicle-road dynamics are being adequately catered for in the design process. Both the travelling comfort of vehicle occupants and the physical performance of the route are improved upon when compared to the types of curves used in current practice. This results from the fact that both the diagrams of the lateral acceleration and the lateral change of acceleration are continuous in the case of the proposed new curve. Lateral acceleration, also called radial acceleration, refers to the acceleration perpendicular to the direction of movement, while lateral change of acceleration is equivalent to the change in lateral acceleration for the purpose of this paper. In the case of the horizontal alignment of a route it is shown that the replacement of combinations of spirals and circular curves with the proposed new curve should be advantageous. There are discontinuities reflected as jumps on the diagram of the lateral change of acceleration of a combined curve in which the spiral curve is used. A method is also deduced of how to design the superelevation along the proposed curve. Equations are derived in order to calculate the maximum values of the lateral acceleration and the lateral change of acceleration in the case of the proposed curve. Taking riding comfort into account, the replacement of the parabolic curve with the proposed new curve should also be advantageous in the case of vertical alignment. In the case of the parabolic curve, discontinuities appear in both the diagram of the vertical acceleration as well as the diagram of the change in vertical acceleration. Equations are derived in order to calculate the maximum values of the vertical acceleration and the change in vertical acceleration on a vertical curve.

• Supplemental Notes:
• The publisher's German name is Forschungsgesellschaft fur Strassen- und Verkehrswesen (FGSV).
• Corporate Authors:

Postbox 50 13 62
D-50973 Cologne,   Germany
• Authors:
• Poolman, P
• Bester, C J
• Conference:
• Publication Date: 2000-6

• English

## Media Info

• Features: Figures; References; Tables;
• Pagination: p. 499-512

## Filing Info

• Accession Number: 00794808
• Record Type: Publication
• Report/Paper Numbers: FGSV 002/67
• Files: TRIS
• Created Date: Jun 28 2000 12:00AM