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== History ==
[[File:Train_Staff_and_Tokens_20151226.jpg |thumb|250px|right|An electric train staff from Bridgnorth (bottom) and original tokens from Sutton Bridge Junction to Coalport (top)]]Early railways used slow speeds and had frequent passing places, so it was safe for trains to be driven 'on sight' as far as the driver could see was clear. Communication between stations to confirm train movements was by means of a of single needle telegraph. This form of working was used when the Severn Valley Railway first opened in 1862.
However as speeds and distances between passing places increased, it was quickly found that more complex systems to avoid collisions were needed on single lines. At first this was done using a unique object called a 'train staff' for each section of line, which the driver of each train was required to carry with him. As there was only one staff for each section, this ensured only one train could be on the line at once. It worked well if trains always alternated in direction, but if two trains in succession were required to travel in the same direction, the token had to be walked back to the start after the first train. To overcome this a ‘divisible’ staff could be used, with successive trains carrying a portion of the staff and no return working being possible until the entire staff had travelled through the section. An alternative was the 'staff and ticket' system; the first train would be shown the staff and given a paper or metal 'ticket' to carry on the engine. The final train of a group travelling in the same direction would carry the staff itself. Staff and ticket working was introduced throughout the Severn Valley Branch in 1891.
