Long distance speed checks must be of Marxist/Leninist origin. It's the same in parts of China.
For example, the expressway from Luzhao that joins the Chengdu/Chongqing expressway is 60 kilometres long. When you collect your ticket as you enter it at Luzhao it has a time stamped on it. The speed limit is 120 kph so if you arrive at the next toll within thirty minutes you get bounced for speeding; 10 yuan/minute, about £1. The result it that as you approach the end there would be all these vehicles either stopped or moving slowly with the drivers looking at their watches.
Never bothered me; a few reminbe here and there, mayo wente.