The Origin Industries standard access tunnel is less a tunnel and more a hole through a ship's internal systems. They are 3'x3', and have direct access to any system it happens to pass by. The only covered part, the floor, has 2.95'x5' panels which can easily be folded upwards (to the side) to access any systems underneath.

There are also vertical access tunnels, with a ladder on one side and a safety line system connected to one side. The ladder has 2 foot sections which can be moved out of the way to access systems, though they must be unlocked manually first.