Heavy rails have high cost performance as they are relatively easy to work on, given that they are the uppermost portion of tracks. However, if we were to make only the rails heavy, the rail axial compression force brought about by temperature changes would increase, possibly leading to other problems. Tracks should be strengthened maintaining the ideal balance for all the constituent elements.
Head-hardened rails are an extremely effective long-term measure against rail wear on sharp curves, and are also employed to reduce maintenance costs.
(2) Sleepers
Increasing the number of sleepers is one way to strengthen sleepers. Along curves this is effective against both track deterioration and lateral force and is therefore recommended.
Recently, diminishing forest resources have caused the price of wooden sleepers to shoot up, making them by no means a reasonably-priced material. Steel sleepers have drawn interest as recyclable material, but most sleepers these days are made of concrete. Concrete sleepers have a long service life, are heavy and stable, and are highly resistant to track deterioration. Other advantages include the fact that they are well-matched to continuous welded rails, the use of which is spreading, as will be described later.
In Japan, composite sleepers made of glass fiber and polyurethane resin have been developed, aiming for a sleeper with the same weight as wooden sleepers and the service life of concrete sleepers. Over a 15-year period, roughly 300,000 composite sleepers have been laid, mainly on bridges. Recent surveys indicate that the goal of a 50-year service life appears feasible.
(3) Rail and Sleeper Fastening
For a considerable period of time, cut spikes and screw spikes, depending on the country, were employed as rail and sleeper fastenings. Tie plates are now used to prevent rails from cutting into sleepers and strengthen resistance to lateral force on curves.
The introduction of the concrete sleeper has given birth to a double elastic fastening with superior absorption capabilities for wheel vibration. These fastenings have been acknowledged for features including improved rigidity of track panels and subsequent increased resistance against track buckling, easy management of fastening strength, and effectiveness against electrolytic corrosion for track circuit components and DC electrified sections due to superior electrical insulation. They are now widely used on both concrete and wooden sleepers. Recently, a maintenance-free fastening with no screws was developed, and its use has increased sharply.
