The unevenness of road surface is an important measure of road condition and a key factor in determining vehicle operating costs. A number of instruments have, therefore, been developed for measuring unevenness, which is usually called roughness and standard roughness scales have been established. However, many of the instruments are expensive and complicated to use or require regular calibration. Modified Roughness Indicating machine is a simple machine to measure roughness, also called MERLIN – Machine for Evaluating Roughness using low-cost Instrumentation. The device can be used either for direct measurement or for calibrating other instruments such as the Vehicle Mounted Bump Integrator. The equipment is easy to use, self – calibrating, robust, easily maintained and employs readily available components.