The roughness of particles has also been estimated using a microscope in an early study by Wright (1955). Sieving, although the most common method, does not provide any true measurement of the size of individual particles. The image analysis methods provide detailed information about the geometry of the aggregate particles but only in 2D. The results of manual techniques are affected by human errors and macroscopic roughness analyses are time-consuming. The first attempt to use a 3D-laser scanning technique to study ballast material was made by Illerstro¨m (1998), where he developed a geometrical evaluation method of scanned images. His method yields both reliable and repeatable results. Characterization of roughness of rock fracture surfaces by the scanning technique has been performed by Lanaro et al. (1998) and can be applied to aggregate particles.