Variable speed of light "c"/"c" where "c" is light speed in flat space. Peter Bergmann did not agree with Einstein, but left the dispute out of his earlier book in 1942 to get Einstein’s endorsement. After Einstein died Bergmann wrote a new book in 1968 claiming that vector light velocity could change direction but not speed. This has become a prevailing opinion in science, but not in agreement with Einstein’s unambiguous math. Bergman did acknowledge that the apparent speed of light would change in a gravity field and go to zero at an event horizon as viewed by a distant observer. Max Born agreed
Road speed limits in the United Kingdom change in the crash rate on the M6 in Cheshire or on the M1 in Northamptonshire. Although these 70mph speed limit road signs are normally not used on motorways (the National Speed Limit road sign is normally used, as it makes it more understandable for motorists their maximum speed on the type of vehicle they're using), they have been used on non-motorway special roads within the UK, and across the motorways within Scotland. Speed limit enforcement is used to check that road vehicles are complying with the speed limits. Methods used include Fixed speed cameras, Average speed cameras and also