Racial segregation was the racist policy of forcing different ethnic groups to use different 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. Yasmin Khan was unsure where she ought to sit, noting there was a lack of citizens with Pakistani heritage in Montgomery. She was permitted to sit in the "white" area of the bus on several occasions.
Many other facilities were segregated. A waitress at Slim's Bar refused to serve Ryan Sinclair and Yaz, labelling the former as a "negro" and mistaking the latter for being Mexican rather than a British woman of Pakistani heritage.
The Sahara Springs Motel was also "whites-only", and Ryan and Yas 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 claimed 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 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)
In 1963, a sign hanging in the window of Mrs Smith's Shoreditch boarding-house read "NO COLOUREDS", which Ace seemed to be disturbed by. (TV: Remembrance of the Daleks)