There are some great features in QGIS 2.6 atlas generation. You can for example filter visible polygons using an attribute from the feature controlling the atlas. So I have a full bus routes extent layer, and one with each direction. The two maps are thus filtered by the full extent layer. Data from Transport for London.

My rules look like:
regexp_substr( group,'(\w$)’) = 1 AND regexp_substr( group,'(\w+)’) = attribute($atlasfeature, ‘route’) AND $map = ‘map1′
and
regexp_substr( group,'(\w$)’) = 2 AND regexp_substr( group,'(\w+)’) = attribute($atlasfeature, ‘route’) AND $map = ‘map2′

Thus we can split the features into the two different maps in the composer. We can filter going and return using the “regexp_substr( group,'(\w$)’) = 1”, since our routes are originally names 101-1 for example for the outgoing and 101-2 for the return.

The Vector Map District background map styling is thanks to Ross : https://github.com/mixedbredie/QGIS-styles/tree/master/OSVMD/Greyscale
With slight modifications.

The PDFs turned out quite well due to the vector source data:
London Bus Route 1

The jpgs are not as good, but Flickr provides hosting:
All London Bus Routes