On Google Maps, search for Penny Lane in Burlington.
You will see where the rail line crosses at the intersection
of Penny Lane and Depot St. Follow the rail line north (up)
and you will see it turns to the east (right) and you will see
North Avenue. That street runs above the tunnel. See
details on the tunnel here:
http://en.wikipedia.org/wiki/Burlington_Tunnel" onclick="window.open(this.href);return false;
If you wish to contiue to Essex, it looks like you will
have to head east on some local streets, take US2/US7 N/E
and look for VT #15 east, which roughly paralells the rail
line and you will cross the NECR main line just south of
Essex Jct (Amtrak), which is one block north.
The tunnel info is off the web. I never have personally
visited the tunnel.