Keywords: under sleeper pads, concrete sleepers, concrete bearers, switches and crossings, geodetic surveying, track geometry parameters, track quality.

Two test sections for concrete sleepers and bearers with under sleeper pads were built in the Czech Republic in 2007. The basic motivation for the construction of the test track sections was an evaluation of under sleeper pads' influence on improvement of track quality as a consequence of ballast bed protection against extreme stress. A consequence of the evidence that track imperfections and higher dynamic effects are closely connected together is a progressive deterioration of the track quality, which is characterized by irregular supports of concrete sleepers or even by voiding sleepers, which can vibrate in the ballast bed (so called dancing sleepers). This effect has also been observed for bearers in crossings where unsymmetrical settlement of bearers occurred and resulted in undesirable cant and track twist. Under sleeper pads appear to be a suitable measure for ballast bed protection. The paper comprises experience of under sleeper pads' applications in the Czech Republic. Some positive influence of under sleeper pads on the track quality was observed after six years of monitoring. Some obstacles concern under sleeper pads' installation into switches and crossings are mentioned. Extension of the application of under sleeper pads is expected in the Czech Republic especially for switches and crossings.

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