 This resulted in a typical "waddling", lateral oscillation of "CemFlo" tank wagons.Furthermore, it was a number of other accidents involving suspected poor riding of CemFlo wagons that resulted in progressively more severe speed restrictions being placed on any trains containing this type.At the Thirsk crash, the oscillation built up to such a state that it eventually threw the rear wheel-set of one wagon off the rails, even though the train was travelling below the maximum permitted for four-wheeled wagons.