Although this is easy enough to say, bringing in machines all at once does not necessarily guarantee success. In the recent past, Japan purchased nearly one hundred multiple tie-tampers, some of which became out-of-date before they were even operated. Machines must be introduced with ample preparation time, taking into account improvement of the technological base and operator training.
To use machines effectively, train intervals in which to operate the machines are necessary.
Therefore, for sections where intervals cannot be secured during the day, use during the night-time hours is essential.
4 Countermeasures for Structure Improvement/Modernization
Earth structures and bridges are directly affected by train load.
Earth structures formed by banking and cutting, comprise the roadbed supporting track, slopes, retaining wall, bank protection, side ditches, slope protection, drains and cross drains which cut across earth structures, etc.
Bridges are constructed to cross the rivers or roads, and are classified according to their purpose, dynamic structure and materials.
Tunnels are structures used to make railway trains run through mountain or hills or in the underground.
4.1 Earth Roadbeds
The surface of earth roadheds which contacts the ballast tends to sink because of long years of repeated loads and erosion due to rainfall, causing the ballast to cut into the roadbed and deteriorate. Recently, attention has been given to the close relationship between train running and roadbed surface maintenance as seen by new track deterioration theories which incorporate this phenomenon.
Various improvements are being made in conjunction with strengthening roadbeds. These measures include installing side ditches and drains, ensuring passageways and spaces to place materials for maintenance and track patrols, and particularly for weak roadbeds, improving roadbeds and laying ballast mats.
From the view point of disaster prevention, care must be taken to repair and construct new slope protection, rock fall prevention and bank protection structures in consideration of the constantly changing environment. There is a Japanese proverb which states that "Disaster
