No motor carrier of passengers subject to 49 U.S.C. subtitle IV, part B shall in the operation of vehicles in interstate or foreign commerce provide, maintain arrangements for, utilize, make available, adhere to any understanding for the availability of, or follow any practice which includes the availability of, any terminal facilities which are so operated, arranged, or maintained as to involve any separation of any portion thereof, or in the use thereof on the basis of race, color, creed, or national origin.