(a) Establishment; Reasonableness. - A motor carrier providing transportation of passengers subject to jurisdiction under subchapter I of chapter 135 shall establish through routes with other carriers of the same type and shall establish individual and joint rates applicable to them. Such through route must be reasonable. (b) Prescribed by Board. - When the Board finds it necessary to enforce the requirements of this section, the Board may prescribe through routes and the conditions under which those routes must be operated for motor carriers providing transportation of passengers subject to jurisdiction under subchapter I of chapter 135.