simon wrote:
Just as my train left Leytonstone heading eastbound to Epping
yesterday, I noticed a tunnel that dips down quite sharply on the
westbound side of the track. I don't think that this tunnel would be
visible from a westbound train entering Leytonstone. Just out of
curiosity, anyone know what it might be used for?

Simon.

That is the branch from Hainault and Newbury Park. As you proceed East, the
branch to Newbury Park enters a tunnel on your left and then dives under
the Epping Branch and remains in tunnel until just before Newbury Park. The
Westbound line from there rises out of the tunnel and joins the line from
Epping on the left of that line. Thus, no conflicting movements.

See the route and signalling diagram at :
http://www.trainweb.org/tubeprune/ro...ling%20Diagram


--
Lawrence Myers