Comparing Productivity and Costs of Three Subgrading Machines

Production rates and costs of three forest road construction machines (Ford County 1164 tractor, D4D and D6D Caterpillar bulldozers) were analysed and compared. Results showed that differences in production rates were attributed mainly by the type and the size of the machine, driver's working experience and the nature of the terrain side slope. Compared to other subgrade productivity studies, machine production rates found in this study were considered to be reasonably high. The mean production rates for the D6D, D4D and the County tractor were 129.0 m3/h, 41.0 mVh and 28.1 mVh respectively. High productive time, easily workable soils and few obstacles encountered during earthworks operation were the major factors which contributed to high machine production rates. Cost analysis showed that the higher the machine production rate the lower the subgrading cost and vice versa. The mean production costs for the D6D, D4D and the County were estimated to be US$ 0.49/m3, US$0.79/m3 and US$0.76 /m3 respectively. The estimated machine production costs were more or less the same as those estimated elsewhere. Although low machine production cost is usually the criterion used in choosing the machine to be used for road construction works, this paper recommends that other factors be considered