Geosynthetic reinforced structures are loaded not only under sustained loads, but especially in traffic structures subject to dynamic loading. Response frequencies of 5, 25, 50 Hz are referred from German railroad authorities. For these fre encies tests were designed to investigate the long-term behaviour of geogrids, especially long-term strength. A comparison of specimens loaded with 3 static loads representing upper. lower and mean load of a dynamic cyclic sinusoidal loading and specimens loaded dynamically show creep-deformations slightly higher than those of the static mean load. The tests lasted for 1000 h; i.e. more than 10 millions cycles