AFAIK tunnel track won't do switches, whenever you try to join tunnel track with a switch it changes to a non tunnel track. You CAN fake it tho, make "underground" using static objects for roofs, walls, and/or floors where necessary;
http://forums.flightsim.com/vbts/showpo ... stcount=13
http://forums.flightsim.com/vbts/showpo ... stcount=16
Start with twin tunnel tracks ending at a tunnel twin single track portal, switch to the newcastle dark concrete track (darkest texture that will make a switch) to connect a switch, then at the base of the switch go back to the single tunnel track, add a portal at that end. Cover the whole thing with the tunnel trackless loft, and/or use parts of viaducts and bridge supports for walls and roof sections. Download my "Metropolitan Suburban" route from the file library here, look at the "subway" on that route, which is actually all above ground.
