Numerous maintenance-free track structures have been proposed, tested and laid over the last several decades.
Bridge sleeper tracks for steel bridges that have existed for some time and concrete ballastless tracks employed widely on underground railways have been adopted in countries around the world. However, Japan is the only nation to have actually laid slab tracks, a type of ballastless track, over approximately 2,000 km.
The wide gauge Shinkansen accounts for most of these tracks, but slab tracks are agressively being introduced when elevating or constructing new narrow guage conventional lines, etc. This is proof that Japanese railways keenly feel the need to reduce track maintenance labor.
In the case of the Shinkansen, track repair costs for slab tracks have been reduced to 30%, compared to about 50% for ballast sections. Comparing figures for interest on construction costs and annual expenses including depreciation, slab tracks are also quite feasible for tunnels and viaducts.
However, there are many difficulties with laying slab tracks on lines which are currently in service. Therefore, several types of new prototype track structures which use composite resins and asphalt and which allow work to be performed during short train intervals are being laid and testing is underway. (See Fig. 5.)
3.3 Improvements to Curve Tracks
Curved sections involve similar measures as with straight sections, and suffer from a number of additional problems.
(1) Curve Radius
As described earlier, speed restrictions along curves can be eased under current conditions by improving cars.
The table on the following page shows the results of a comparison of when the existing 400 m minimum curve radius is improved to 800 m and when the curve radius remains the same, but the running speed is increased 15 km/h due to car improvements, over a double- track section roughly 350 km in length.
In this case, the speed through curves after making car improvements is far more advantageous than implementing improvements to curves.
