The transport tunnels are used for the maintenance of the three particle accelerators. They radiate from the Bona reactor, but there are access points scattered over the islands (the hatches are locked with code locks), and then there are the north, west, south and east gates.
ETA: The service tunnels are also accessed from buildings that look somewhat odd (p. 70 in the art book).
In the tunnels, a narrow-gauge railway allows for transport of materiel and personnel. The tunnels allow for vehicles like the "Sätuna Spiders" (p. 90-91 in the art book), at least in some sections.
The public roads on Munsö and Adelsö are connected by a ferry (see pic in a post above), and not a tunnel. https://firstname.lastname@example.org, ... !1e3?hl=en
My life fades. The vision dims. All that remains are memories. I remember a time of chaos, ruined dreams, this wasted land.