Investigation into the effect of moisture on rail adhesion

This paper presents the results of a study, funded by RSSB on behalf of the Adhesion Research Group and the Vehicle Track System Interface Committee, into the effect of the presence of moisture at the wheel/rail interface during dew and damp conditions. Arup and the University of Sheffield have collaborated to perform a comprehensive and detailed review of the current body of knowledge in this area and an analysis of the latest relevant operational performance data. For the purposes of the assessment of data the study has utilised a proven methodology (based upon the approach of the National Intelligence Model) to assess the quality and relevance of the information based on profiling each piece of 'evidence' related to wet-rail syndrome. The evidence was categorised and a knowledge map produced which shows the position of each piece of evidence (based upon its topic). In addition extensive performance data was analysed from a variety of sources. The available written evidence is well supported by information derived from performance data records and has led to the development of the following evidence based definition: Wet Rail Phenomenon: Poor adhesion conditions caused when low levels of moisture are present at the wheel/rail interface. These conditions are associated with dew on the rail head, very light rain, misty conditions and the transition between dry and wet rails at the onset of rain. They are not necessarily associated with the additional presence of other (non-water) rail head contaminants.