So-called base tunnels (longer, lower tunnels to replace existing tunnels or long climbs up to the crests of passes) are all the rage in Europe currently. A number of very long rail tunnels are in various stages of construction or planning in various European countries. These tunnnels will be at or near the top of the list of the world's longest rail tunnels.

The problem with very long tunnels and diesel operations (in the U.S.) is, of course, ventilation. The longest U.S. rail tunnels -- Cascade, Flathead, Moffat -- are somewhat at the limits of what can be ventilated reasonably efficiently. And even there, the ventilation process is a substantial capacity inhibitor.

In Europe, of course, the predominant form of railroad motive power is electric. The new base tunnels are all twin-bore, with directional running in the bores, which makes them somewhat self-ventilating, though there is usually some provision for supplemental ventilation. Like the Chunnel (Channel Tunnel) these long base tunnels will all have one or more emergency cross-overs deep within the tunnel, but these are intended primarily for a shorter segment of track being taken out of service for maintenance.

New Europe-wide safety regulations have mostly ruled out any lengthy double-track tunnels, as any major incident in such a tunnel would effectively take both tracks out of service and would make it more difficult to evacuate passengers and crews.


This is not to say that the case could not be made for new base tunnels in the U.S. Though the Moffat route is a favorite place for me to visit, I've also long thought that this area is a perfect example of the case for a twin-bore base tunnel. Yes, you'd lose a lot of scenic track, but a lower tunnel would undoubtedly be more efficient for freight transportation. And, at some point, I think the U.S. railroads will have to revisit the the question of substantial new mainline electrification.

The bottome line, then, is the cost of these tunnels. In Europe, the governments of various countries see these new base tunnels as a good investment in their transportation future. So, most of the cost is being covered by the government(s). Certainly, the costs of a major new base tunnel would be difficult to afford/justify for even the largest and most affluent U.S. railroads -- even though they would be a good long-term investment.

Much is going to depend on whether the U.S. ever gets any kind of nationa transportation policy that reccognizes that there are only so many interstate highways you can build and that even widening then has its limits.

-- Ernest