Road alignment and gradient issues in the maintenance of logging roads in Tanzania.

In forestry, roads are essential structures as they provide access to the forest from the establishment phase to harvesting stage. Thus it is important that roads are properly planned, constructed and maintained in order to ensure easy access, smooth transport of forest products, safety, comfort and economy on vehicle operations. For Tanzania where commercial timber harvesting in plantation forests has just started, appropriate values of parameters for road alignment and gradient, in the context of the country's settings, need to be established. This study, which was carried out on a gravel secondary access road, established that traffic and water contribute significantly to road deterioration or loss of road surface materials. Road alignment and road gradient were found to influence the rate of soil loss. The study found that the optimal road grade and curve radii which minimized road maintenance cost in this area were grades less than 6% and radii above 100m respectively. Statistical analysis however showed that there was no significant difference between straight sections of the road and the curve sections in terms of loss of surface layer materials.