Dust generation by vehicles on unsealed roads can cause serious air pollution, reduce visibility and the safety of motorists, pedestrians and workers and pose an overall hazard to health. Prior to the development of a road dust monitor, dust levels were either subjectively judged on a scale of one to five by the driver of the vehicle or by an observer at the roadside, or dust was collected in receptacles and then weighed. For obvious reasons, these methods are unacceptable for the monitoring of the effectiveness of dust palliatives or for the determination of acceptability criteria for dust on unsealed roads. A vehicle-mounted dust monitor was developed at the CSIR to quantify road dust levels. This dust monitor, which incorporates an infra-red measuring system, was developed in three phases over a four year period. A statically mounted system was developed for use on very rough roads, underground haul roads and sections where dust needs to be measured over extended periods. Road roughness contributes significantly to vehicle operating costs and is therefore used to determine optimum maintenance intervals. Accurate measuring equipment is required for experimental work to develop deterioration models and to compare the performance of stabilised sections. In South Africa, a Linear Displacement Integrator (LDI) has been used for roughness measurements. However, this equipment is relatively expensive, vehicle dependant and generally unsuitable for accurately measuring short experimental sections. The CSIR therefore identified the need for a low-cost road roughness integrator (LORRI) for use in areas where it is not feasible to use an LDI. The LORRI incorporates a frame with front and rear wheels. A trailing arm with a measuring wheel is attached to the front wheel. A linear potentiometer connected between the frame and the trailing arm measures vertical movement and hence the road roughness. Speed and distance travelled is determined with a metal detection and sensor system. Data is processed on a data acquisition system and information is displayed and stored on a notebook computer. Repeatability tests and a comparison with an LDI were carried out on road surfaces of varying roughness. The repeatability of the measurements were considered acceptable and the comparison of the LORRI measurements with those of the LDI correlated well. The LORRI can be used where traditional equipment is not feasible nor cost-effective, for quality control of labour intensive and community based construction and maintenance and calibration of LDI equipment. (A)
Samenvatting