There is an extremely high standard of mapping available in the UK and we are very lucky to be able to use highly detailed Ordnance Survey maps wherever we go. With practice these maps can tell us everything we need to know to get ourselves from A to B safely. However one area that often seems to cause confusion is the different ways paths are marked on Ordnance Survey maps; a better knowledge of when each symbol is used will soon improve your ability to find your way across the hills.
On a 1:25,000 Ordnance Survey map public rights of way in England and Wales are marked with green dashes (short dashes for footpaths and long for bridleways) but it is very important to remember that this means only that there is an ancient common law right to pass along this route at all times. It does not mean that you will necessarily be able to see the path and be able to follow it. Definitive maps of the rights of way were drawn up by county councils in the 1950s and many of these paths are now long since disused and overgrown and, even in good visibility, can be difficult or impossible to find.
Other paths which are not designated rights of way are marked on the Ordnance Survey maps as short black dashes. If these paths are within the newly designated access land you are perfectly within your rights to walk along them. These paths are marked on the map because at the time of the aerial survey used to create this map they were visible on the ground; they have usually been made by thousands of feet walking along the same line. They are often the most direct route from summit to summit or from the summit to the valley because they have been created by humans going where they want to go.
For hill walkers the problem with this system is that the green dashes of the public highways stand out clearly on the map and often give the impression that these paths are more important or bigger than the black dashed paths, however often the opposite is true. You should never assume that a path is going to be easy or even possible to find but this is particularly true for the public rights of way. A black dashed line on the other hand tells you that particular path was visible on the ground at the time of making the map and chances are it still is.
When following any path you should continually compare the map to the ground you are covering to make sure the path really is going the same way as the dashes on the map. Paths change over time and could have changed since your map was last updated. Do not rely on paths and always be prepared to use a compass if the path you are following disappears or goes off in the wrong direction.