COMPUTER AIDED OPTIMISATION OF HIGHWAY ALIGNMENT

This paper presents an Indian study to show how the optimisation of vertical alignment could reduce road construction costs. The geometric design standards, suggested by the Indian Roads Congress for rural roads, were considered in the programme development. The main area where optimisation can reduce costs is earthworks, which are about 25% of total construction costs. The paper describes the computer aided road design technique, and the development of the FORTRAN optimisation software. The following conclusions are drawn: (1) substantial benefits can be obtained from optimisation, and the value of optimisation techniques in reducing costs should be recognised in road planning and design: (2) optimisation of vertical alignment can significantly reduce the costs of road construction; (3) dynamic programming has been found to be a more suitable technique for optimising road alignment; (4) this limited study has not found the cost of vehicle operations to be a significant factor in optimising vertical alignment; (5) in a country like India, where highways are the major mode of transport and economy the main criterion for their development, optimisation will contribute many tangible and intangible benefits to road users and nonusers.