The alignment chosen for a new road will affect the travel costs of all drivers using it. In current practice, travel costs are taken into account when making an economic evaluation of a new road but are often not included explicitly when designing the alignment of the road. This inconsistency may lead to the construction of a new road to a design which does not represent the best balance between the costs of travel and of construction. In this report a simple method is described for allowing the expected travel costs of a new road to influence the design of the alignment. The conversion of an existing vertical alignment optimisation computer program to take account of travel costs is described. The new program has been applied to a current highway scheme with a vertical alignment that had been optimised to minimise the scheme's construction cost. The highway considered passes through hilly terrain, and it is shown that an improvement in the economic value of the scheme can be achieved by introducing travel costs into the design process. (Author/publisher)
Abstract