Speed of light less uncertain than the previously accepted value. The remaining uncertainty was mainly related to the definition of the metre. As similar experiments found comparable results for "c", the 15th General Conference on Weights and Measures in 1975 recommended using the value for the speed of light. In 1983 the 17th CGPM found that wavelengths from frequency measurements and a given value for the speed of light are more reproducible than the previous standard. They kept the 1967 definition of second, so the caesium hyperfine frequency would now determine both the second and the metre. To do this, they redefined the
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