The first part of this leaflet deals with civil engineering means of improving the track formation on existing lines. The second part describes the various working methods. The third part evaluates these working methods in respect of operating and civil engineering conditions, staff and machine cost, performance and quality of work. Diagnosing the need for improvement of track formation, also the selection and dimensioning of the materials to be incorporated, are dealt with in UIC Leaflet 719 . With a strict interpretation of the diagnosis, improvement of the formation is often necessary only for relatively short sections of line. However, it should be noted that, for reasons of uniformity and to prevent problems at transition points, short untreated sections between two improved sections should be avoided.