A new method for estimation of critical speed for railway tracks on soft ground

This paper presents a new method, ETL (EBER Track Lab), which allows for estimation of critical speed from measurements from a running train at normal speeds. Hence, large distances can be covered in short time. The method is based on the idea that the dynamic amplification, and the change of shape of the displacement curve under the loaded axle, starts already at speeds well below the critical speed. By observing the change in the displacement curve and comparing it with the results from a theoretical model one can derive an estimate of critical speed. The method has been validated by calculations and test runs. Both the measurements and the calculations show that ETL can give a reasonable estimate of the critical speed from a measurement speed of 0.4 times the critical speed or higher. The method has been applied for inventory measurements on the main network in Denmark.