a method is described for designing automatically the vertical alignment of a road which is an improvement on that described in an earlier report. the ground longitudinal section is smoothed to obtain a line which is similar in shape to the desired final vertical alignment. this line is broken down into summit and sag curves to which parabolic curves are fitted. the parabolic curves are joined by tangent lines to form a conventional vertical alignment. this alignment is then modified to obey any constraints which may be imposed by the engineer. as this modification tends to pull a vertical alignment away from the ground longitudinal section, the fitting of the alignment to the ground is then improved. a computer program (venus 11) is described, which uses this method of designing a vertical alignment and the experience gained using this program is discussed. a version of the program is available for limited use and, after further development, will be published for general distribution. the work is part of a wider study of the application of optimization techniques to road design which is being carried out at the transport and road research laboratory. (a)

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