Having a love for all things tube map, I decided to do a bit of exploration, below are some initial experiements.
Tubes into a bottle:
Tube map with only the national rail logos exposed.
using the tube lines as a guide, I created the patterns. I created patterns using the structure of the tube map, for instance the northern and central lines connect. As do the circle and district and hammersmith and circle.
northern and central line combination.
overground, central and northern lines.
hammersmith and circle.
circle and district