Improvements to Sight Distance Algorithm
Publication: Journal of Transportation Engineering
Volume 127, Issue 4
Abstract
This paper describes improvements developed for an existing algorithm that calculates sight distance profiles based on horizontal geometry. Exact expressions are developed for vector derivatives for plane curves including clothoid spirals. Coordinate and derivative vectors are developed for partial spirals that possess nonzero curvature at both ends, frequently used as transitions between circular curves of different radii. As with complete spirals, the coordinate vectors are approximate and the derivative vectors are exact. Finally, an exact method for measuring distance along an offset curve to a clothoid spiral is developed. Taken together with the results in a previous referenced paper, this represents a complete recipe for computing sight distance profiles along arbitrary horizontal alignments. A numerical example is included to illustrate the use of the algorithm.
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References
1.
American Association of State Highway and Transportation Officials (AASHTO). ( 1994). A policy on geometric design of highways and streets, Washington, D.C.
2.
Hassan, Y., Easa, S. M., and Abd El Halim, A. O. ( 1996). “Analytical model for sight distance analysis on three-dimensional highway alignments.” Transp. Res. Rec. 1523, Transportation Research Board, Washington, D.C., 1–10.
3.
Kreyszig, E. ( 1959). Differential geometry, University of Toronto Press, Toronto, Canada.
4.
Lovell, D. J. (1999). “Automated calculation of sight distance from horizontal geometry.”J. Transp. Engrg., ASCE, 125(4), 297–304.
5.
Lovell, D. J., Jong, J.-C., and Chang, P. C. ( 2000). “Generating sight distance profiles for arbitrary horizontal alignments with nonuniform lateral clearance.” Proc., 2nd Int. Symp. on Hwy. Geometric Des., Forschungsgesellschaft für Straßen- und Verkehrswesen e.V., Köln, Germany, 422–433.
6.
Taiganidis, I., and Kanellaidis, G. (1999). “Approximate perspective design of roads.”J. Transp. Engrg., ASCE, 125(4), 314–323.
Information & Authors
Information
Published In
Journal of Transportation Engineering
Volume 127 • Issue 4 • August 2001
Pages: 283 - 288
History
Received: Mar 3, 2000
Published online: Aug 1, 2001
Published in print: Aug 2001
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