| dc.description.abstract | Road gradient being one of the features guided by geometric design policy, is the end result of an evaluation of the benefits and costs associated with alternative route locations with due consideration given to existing terrain, safety, construction haulage and cost (Tang et al., 2018). Vehicle operating costs are among the various factors that need to be considered in coming up with an economic, yet viable design for a proposed road. However, more focus is put on trying to minimise costs of cut and fill during construction, and little emphasis is put on achieving the vertical gradients specified in design manuals in Uganda which in turn affects the costs borne by the users of the road through reduced vehicle speeds leading to increased travel time and fuel consumption. This research investigated the effect of road gradient on vehicle operating costs on Kampala Entebbe road-Zzana Kajjansi road section and Kitala Gerenge road. Relationships between road gradient and vehicle operating costs were established based on the multivariate model of the Caribbean study from HDM-4 and the Operating speed-cost relationships obtained from DeWeille. Generally, the vehicle operating costs increased quadratically with the rate of change of vehicle operating costs with road gradient increasing at a constant rate. Along the Kitala-Gerenge road, changes in terrain from flat to rolling along ascents led to percentage increases in vehicle operating costs of 2.43%, 1.11% and 0.50% for Commercial vehicles, Light Commercial Vehicles and Passenger cars respectively. In addition, changes in terrain from rolling to mountainous led to percentage increases of 9.42%, 3.79% and 1.73% for Commercial vehicles, Light Commercial Vehicle and Passenger cars respectively. Changes of terrain from mountainous to escarpment led to percentage increases of cost 13.90%, 4.96% and 2.31% respectively for the vehicle categories. Along the Zzana-Kajjansi road, changes in terrain from flat to rolling along ascents led to percentage increases in vehicle operating costs of 2.26%, 1.080% and 0.53% for Commercial vehicles, Light Commercial Vehicle and Passenger cars respectively. In addition, changes in terrain from rolling to mountainous led to percentage increases of 8.94%, 3.70% and 1.81% for Commercial vehicles, Light Commercial Vehicle and Passenger cars respectively. Changes of terrain from mountainous to escarpment led to percentage increases in vehicle operating costs of 13.49%, 4.86% and 2.40% respectively for the vehicle categories. With vehicles descending along Kitala-Gerenge road, changes in terrain from flat to rolling led to percentage increases in vehicle operating costs of 1.28%, 0.87% and 0.43% for Commercial vehicles, Light Commercial Vehicle and Passenger cars respectively. In addition, changes in terrain from rolling to mountainous led to percentage increases of 4.60%, 2.93% and 1.51% for Commercial vehicles, Light Commercial Vehicle and Passenger cars respectively. Changes of terrain from mountainous to escarpment led to percentage increases of cost 6.36%, 3.77% and 2.04% respectively for the vehicle categories. Vehicles descending along Zzana-Kajjansi road experienced approximate changes in percentages in vehicle operating costs of 2.37%, 0.85% and 0.46% for Commercial vehicles, Light Commercial Vehicles and Passenger cars respectively. In addition, changes in terrain from rolling to mountainous led to percentage increases of 8.00%, 2.86% and 1.58% for Commercial vehicles, Light Commercial Vehicle and Passenger cars respectively. Changes of terrain from mountainous to escarpment led to percentage increases in vehicle operating costs of 10.05%, 3.69% and 2.12% respectively for the vehicle categories. Generally, the vehicle operating costs percentage increase was higher along ascents compared to descents and changes in costs were more prominent in Commercial Vehicles compared to Light Commercial Vehicles and Passenger cars in that respective order. | en_US |
