Ref :
http://content.tfl.gov.uk/london-overground-network-map.pdf
Tunnels: http://content.tfl.gov.uk/tube-map-with-tunnels.pdf
Ref :
http://content.tfl.gov.uk/london-overground-network-map.pdf
Tunnels: http://content.tfl.gov.uk/tube-map-with-tunnels.pdf