Here's a list of the tunnels for the RC-XD Car in Call of Duty: Black Ops that have been found. You can find the original post
here.
Grid: Section C2 at the bottom of a wall. This tunnel is the one with the most options. About halfway through there is an intersection where you can go left or right to go outside or upstairs into a building. You can also continue to go straight.
Hanoi: Section B4, B3, C3, C2. There is a tunnel going under the building in B4 to section B3. The tunnel in section C3 is underneath the stairs and exits in section C2 underneath the stairs there. The C3 - C2 tunnel is great for catching enemies in the center courtyards.
Nuketown: Section B2 to D2. This is probably the best path even though it is not a tunnel. Start at either fence opening at B2 or D2 and boost (LB) over the rock jump. This will catch multiple enemies by surprise because they most likely just spawned.
Radiation: Section C4 to multiple other sections. This is the most diverse tunnel I have found. It goes to the underground section of this level where you can continue across the underground into another tunnel and out to the other side of the level.
WMD: Section C3. The tunnel is in the second story of the building in C3. It is one of the shortest but really effective. It goes through a short air duct and out the side of that building.
Linear Mode
