DC systems (especially third-rail systems) are limited to relatively low voltages and this can limit the size and speed of trains and cannot use low-level platform and also limit the amount of air-conditioning that the trains can provide. This may be a factor favouring overhead wires and high-voltage AC, even for urban usage. In practice, the top speed of trains on third-rail systems is limited to 100 mph (160 km/h) because above that speed reliable contact between the shoe and the rail cannot be maintained.
What is the speed limit for third rail system trains?
160 km/h

In 1899 the state legislature passed a new constitution, with requirements for poll taxes and literacy tests for voter registration which disfranchised most black Americans in the state. Exclusion from voting had wide effects: it meant that black Americans could not serve on juries or in any local office. After a decade of white supremacy, many people forgot that North Carolina had ever had thriving middle-class black Americans. Black citizens had no political voice in the state until after the federal Civil Rights Act of 1964 and Voting Rights Act of 1965 were passed to enforce their constitutional rights. It was not until 1992 that another African American was elected as a US Representative from North Carolina.
What year was the Federal Civil Rights Act?
1964

During George's reign the break-up of the British Empire and its transition into the Commonwealth of Nations accelerated. The parliament of the Irish Free State removed direct mention of the monarch from the country's constitution on the day of his accession. From 1939, the Empire and Commonwealth, except Ireland, was at war with Nazi Germany. War with Italy and Japan followed in 1940 and 1941, respectively. Though Britain and its allies were ultimately victorious in 1945, the United States and the Soviet Union rose as pre-eminent world powers and the British Empire declined. After the independence of India and Pakistan in 1947, George remained as king of both countries, but the title Emperor of India was abandoned in June 1948. Ireland formally declared itself a republic and left the Commonwealth in 1949, and India became a republic within the Commonwealth the following year. George adopted the new title of Head of the Commonwealth. He was beset by health problems in the later years of his reign. His elder daughter, Elizabeth, succeeded him.
In what month and year did George VI discontinue using the title Emperor of India?
June 1948