- American Underground-Construction Association
- Promoting the design, development, construction, and use of underground facilities. - International Tunnelling Association
- Encourages planning of the subsurface and promotes the use of tunnels. - MrTunnel
- Includes reports on major United States road tunnel projects. - Tunnelbuilder
- Features news reports of projects worldwide, and tunnel building dreams, errors, and horrors. - Norwegian Tunnelling Technology
- Covering history, projects, products, research, and development. - Tunnel Page
- Directory of the world's longest tunnels, subsea tunnels, immersed tubes, railway tunnels, and old tunnels. - U.S. Federal Highway Administration - Tunnel Engineering
 - FAQ - Transit Tunnels
- Tips for exploring them on foot.
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