"Andy Champ" wrote in message
. uk...
On 01/01/2012 18:30, dennis@home wrote:
Its cheaper to bore one tunnel these days.

It's always been cheaper.

I know.


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...

We know that too.