The four years of experience to date with the use of frame sleepers on ballasted track have shown that this design offers enormous advantages in terms of carrying capacity and form stability. This is the result of a substantial increase in the sleeper-ballast contact area that has even been enhanced by the installation of resilient pads. The much slower rate of deterioration of track geometry observed confirms theoretical work to date, which pointed to substantial reductions in maintenance requirements. The longer useful life that may be deduced from this is synonymous with considerable economic advantages in life cycle costs, even if the cost of procuring frame sleepers according to current prototypes remains more expensive than for standard sleepers. To drive costs down it is necessary to manufacture in larger numbers but further savings are also possible through design adaptation. Overall it is true to say that this type of sleeper is likely in future to represent an alternative way of strengthening ballasted track to cater to higher axle-loads and speeds.
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