Final answer:
The Jim Crow laws provided for the 'separate but equal' doctrine, allowing racial segregation in public and private facilities, including transportation, as upheld by the Supreme Court in Plessy v. Ferguson.
Step-by-step explanation:
The term that allowed passengers to sit in 1st class and refrigeration cars based on racial segregation was the Jim Crow laws. Specifically, the Supreme Court case Plessy v. Ferguson upheld the legality of these laws by establishing the doctrine of "separate but equal" in 1896. These laws mandated the separation of races in various public and private areas, including transportation, and were considered constitutional until they were overturned by subsequent court cases such as Brown v. Board of Education in 1954, which began the process of desegregation.