Racial segregation was the racist policy of forcing different ethnic groups to use separate facilities from each other. Segregationist policies were common in several US states in the 1950s, such as Alabama and Mississippi. (TV: Rosa) It was also permitted in the United Kingdom up to at least the 1960s. (TV: Remembrance of the Daleks)
By 1943, Montgomery, Alabama, had a segregated bus system. Black passengers had to enter through and sit at the back, while white passengers could sit at the front. The sections were determined by movable signs, according to the needs of white passengers. If white people needed the seats in the middle, black passengers had to move back in the bus, by law.
The Sahara Springs Motel was also "whites-only". Ryan and Yaz had to join the Thirteenth Doctor and Graham O'Brien in their room through the back window. During an inspection by Police Officer Mason, he made clear that it was a criminal offence to harbour non-white individuals on segregated premises.
On 1 December 1955, Rosa Parks famously refused to give up her seat to a white passenger, Graham, on a segregated bus, an event witnessed by the Thirteenth Doctor, Ryan and Yaz. She was arrested, and the following Monday, the Montgomery Bus Boycott began. As a direct result, the racial segregation of buses in Montgomery ended on 21 December 1956, ushering in the Civil Rights Movement. (TV: Rosa)