(a) This subpart sets forth segregation requirements in addition to any segregation requirements set forth elsewhere in this subchapter.

(b) Hazardous materials in limited quantities when loaded in transport vehicles and freight containers, are excepted from the segregation requirements of this subpart and any additional segregation specified in this subchapter for transportation by vessel; except that articles of division 1.4, compatibility group S, shall not be stowed in the same compartment or hold, or cargo transport unit with hazardous materials of Class 1 of compatibility groups A and L.