"polygonum" wrote in message
news
On Mon, 02 Jan 2012 20:39:44 -0000, dennis@home
wrote:



"Terry Casey" wrote in message
...
In article ,
lid says...

On 01/01/2012 18:30, dennis@home wrote:
Its cheaper to bore one tunnel these days.

It's always been cheaper.

But two tunnels gives you an escape route via cross passages. It help
prevent collisions. It takes away the drag from passing trains.

And BTW you can profile them differently for acceleration...


Isn't that how this argument started ...?

No. It started when I said a single large tunnel is cheaper than two
small ones.
Cheaper may not mean better it depends on the requirements.

And no-one has yet pointed out the obvious issue of the geology which
might overwhelm the other issues.

Geology is covered by requirements about which I have stated on several
replies.