In 1987, a research project on gravel roads was established in thailand between the thailand office of accelerated rural development(ard) and the overseas unit of the u.K. Transport and road researchlaboratory (trrl). The principal objective was to compare the effects of alternative maintenance strategies for unpaved roads in wet regions. The project also studied the relative performances of motor graders and tractor-towed graders for maintaining roads carrying traffic volumes of 50 to 300 vehicles per day. The potential benefits are the optimization of grading frequencies for different levels of traffic. In addition, the opportunity was taken to evaluate the applicabilty of trrl prediction models for gravel road deterioration produced from data obtained in dry and temperate regions to roads in wet climates. Preliminary results from the study suggest that tractor-towed graders can achieve similar reductions in roughness to those obtained with the motor grader. Running costs of the tractor-towed grader units are less than half those of the motor graders. If investment and depreciation costs are considered, then the savings in maintenance costs are substantially higher. An additional problem in thailand is that of maintaining rural roads built in hilly terrain with gradients up to 17%. The ard has investigated methods of reducing the high maintenance costs on such roads and found that the most cost-effective solution was to surface the most vulnerable lengths of road with concrete blocks. After 2 years' trafficking, this treatment hasproven to be highly cost-effective, requiring no maintenance despite heavy rainfall. This paper appears in transportation research record no. 1291, Fifth international conference on low-volume roads, may19-23, 1991, raleigh, north carolina, volume 1.
Samenvatting