In the early years of British Railways following nationalisation in 1947 there was a rapid development in modern traction in both the diesel and electric fields.  As part of this development there was considerable information around the deign and performance of the various new locomotives and multiple units in the form of technical reports which were often available to either the public or the various technical societies.  Over the years this information became increasingly difficult to source without considerable research.  In addition as commercial interests became more important the free sharing of information became increasingly restricted by the various manufacturers.  This was further entrenched with the onset of the railway privatisation from 1994.  

A further problem is that the various curves were often printed in low definition and the ability to accurately read data was extremely difficult.  

It is the intention of this site that the sources of information collected by the author over many years will be presented in a uniform manner which enables the information to be accurately read. The author uses the scans the graph at a fairly high resolution and then uses the "DataGrab"software to digitise the curve.  The curve is then redrawn at a consistent resolution and added to the  datapage.  The digitised data is also presented in tabular format.  Were it is possible the source of the data is provided however there are a few occasions when the author has been requested to withold the original source.  If there are any obvious errors in the data these are highlighted in the text.  The various technical curves are provided in approximate chronological order for the early designs followed by Class order for the remainder.  A few curves are provided for overseas traction