Just found this picture of the Birkenhead Tunnel on another site. You may of seen it before but if you haven't it's quite good cross section of how it works. Enjoy!!

Click the Link

Interesting. I'm sure I've seen that before. Here's a very similar, but not identical, one from the book "The Mersey Tunnel" issued by the Mersey Tunnel Joint Committee. Undated.

Is number 12 that closed of bit? Corpy rd ish not been that way for years

Yes, No.12 is the now closed dock branch. Exit at Rendel St.

It's only closed because Mersytravel decided that they don't want to make the tunnels free to use as they were originally intended to be!

I can't see the connection.

The volume of traffic is such that the idea of a junction controlled by traffic lights just wouldn't work. This is the reason that the Liverpool dock branch is exit only.

Good illustration but the tunnel meanders all over the place when you drive down it. The picture makes it look pretty straight.