The roughness of a road's surface is an important measure of road condition and a key factor in determining vehicle operating costs.A simple roughness measuring machine has been designed especially for use in developing countries. It is called merlin (machine for evaluating roughness using low-cost instrumentation). The device can beused either for direct measurement or for calibrating response-typeinstruments such as the vehicle-mounted bump integrator. It consists of a metal frame 1.8 M long with a wheel at the front, a foot at the rear, and a probe midway between them that rests on the road surface. The probe is attached to a moving arm at the other end of whichis a pointer that moves over a chart. The machine is placed at successive locations along the road and the positions of the pointer are recorded on the chart to build up a histogram. The width of this histogram can be used to give a good estimate of roughness in terms of the international roughness index. Calibration of the device was carried out using computer simulations of its operation on road profiles measured in the 1982 international road roughness experiment. The merlin is in use in a number of developing countries. It can usually be made locally at a current cost of typically u.S. $250. This paper appears in transportation research record no. 1291, Fifth international conference on low-volume roads, may 19-23, 1991, raleigh, north carolina, volume 2.
Abstract