a method for designing automatically the vertical alignment of a road is described. the ground longitudinal section is smoothed to obtain a profile which approximates to the final road line. this profile is broken down into summit and sag curves by finding the points where it intersects with another line which is obtained by carrying out a more severe smoothing of the ground. tangent lines and parabolic curves are then fitted to the summit and sag curves of the profile to form the preliminary vertical alignment. violated constraints on the level of the road are expressed as an objective function which is minimized using a direct-search optimization technique and other constraints which are violated by the alignment are satisfied using a variable- elimination technique. extra vertical curves are added where needed. a computer program (venus 1) is described which uses this method of designing a vertical alignment and some of the experience gained using this program is discussed in a case study. further development of this program to provide an alignment which follows the ground more closely will be described in a subsequent report. 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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