A method of routing a new pipe duct into an existing pressurized gas pipeline includes the step of introducing a translating member into the pressurized gas pipeline via an entry port in a first fitting attached to the pressurized gas pipeline. The translating member, such as a duct rod, is advanced within the pressurized gas pipeline by a driving mechanism, until it reaches second fitting. The translating member is attached to a pipe inner duct. The duct rod and pipe inner duct are then pulled back through the pressurized gas pipeline by the driving mechanism.