The Effect of Vertical Alignment Design Standards Upon the Energy Costs of Inter-Urban Roads.

This thesis describes the results of an investigation into the effects of vertical alignment design standards upon the energy costs of constructing and operating major rural roads in the United Kingdom. Alternative road designs have been produced for a series of ground profiles, and for each of these designs the energy costs have been calculated. The construction energy cost has been calculated from the fuel consumption and production output of earthmoving plant. The energy costs of structures and surfacing was assumed to be constant for the design changes examined. The energy costs of operation were calculated from the results of fuel consumption tests undertaken by the author. These tests showed a clearer and more accurate relationship between gradient and fuel consumption than other tests undertaken in the United Kingdom. The alternative designs produced examined the effects of altering the standards for maximum gradient, minimum curve radii and length, formation width, minimum gradient, and side slope gradient. The effect of choosing an alternative route was also investigated. The results of the energy calculations for these alignments showed that in general, the more constrained the design, the lower the total energy costs. This conclusion is insensitive to changes in construction cost, but is highly sensitive to changes in vehicle numbers or types. For a motorway type design, the average flow on trunk and motorway roads, and a thirty year design life the maximum gradient standard that produced the minimum energy cost was about 1. 5 percent. This is considerably lower than used at present, and the most recent standard encourages the use of steeper gradients. This research suggests that vehicle operating costs are an important factor when designing the vertical alignment of a road, and that present methods do not accurately determine the effects of road design on vehicle costs