The surface evenness of roads is often measured with the Bump-Integrator, a device that sums displacements between a test wheel and its chassis. To improve the accuracy of measurement on short sub-sections of road a microprocessor-based integrator unit has been developed. The unit replaces the mechanical integrator fitted to the trailer of the standard Bump-Integrator. The new equipment enables the unevenness index of sub-sections as short as 30m to be measured with an accuracy of better than 3 per cent. This accuracy on short sub-sections makes the Bump-Integrator suitable for use with the CHART highway maintenance system. The report describes the new equipment and the tests conducted to validate the microprocessor integrator unit. Factors affecting the accuracy of measurement are examined and details of the range of facilities provided are given. These include the automatic measurement and recording of consecutive sub-sections, speed correction and identification of the location of large irregularities in the road surface. The dynamic characteristics of the Bump-Integrator can also be checked with the new equipment. (A)

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