| This research includes the development of an innovative representation of topography, a detailed analysis of its implication in facility routing, and the development of a substantially improved technique to determine bridge, culvert, and tunnel requirements.;The practical problem of alignment choice for a transportation facility is analyzed by introducing an abstract form of drainage basin model and a global approach to solve the alignment problem. A procedure to determine the optimum alignment is presented by dividing this problem into three nested choices: the first order horizontal alignment, the second order horizontal alignment, and the vertical alignment.;A terrain model is created based on an idealized geometry of a drainage basin consisting of ridges, streams, and a major river valley. The geometry is defined by a set of six descriptive parameters, and solved using trigonometric relationships. A construction cost model is developed based on the geometric abstraction of the terrain model and is combined with a vehicle operating cost model which is mostly based on previous research. The modeling technique used provides a general approach for modeling major structures by furnishing criteria for structure type selection and procedures to determine the site-specific requirements for bridges and culverts.;The important factor for determining a transportation facility alignment through any basin in the relative importance of construction versus operating cost. The key element in this cost trade-off is the level of traffic on the facility. The analysis reveals that, once a moderate traffic volume is achieved, there are several ways to build a transportation facility which are very close to optimum. Hence, even though the traffic or input prices may vary from forecasts, the impact on the optimum solution is likely to be minor. |
