Unsuccessful vs successful metric
For a moment take away the argument of whether metric/SI is good or bad ....... In Australia and New Zealand beginnning in 1966 and ending in late 1970s, currency was changed (1966), then temperature (1969), ALL road signs changed (1973) in NZ in conjunction with the Oil shock which meant 60 mph was temporarily replaced by 80 km/h (50 mph) which we had to put up with for many years afterwards until in the late 80s when we finally got 100 km/h as a max. speed limit. Metric weights and measures were phased in for a few years only from 1974 to 1977/78 and absolute compliance was expected after that. Builders changed to metric, land has been measured in metric since 1975 or so ..... Holy smoke, was it popular? Not always probably, but it was done successfully with no double-up mess like you have in the UK. Since the late 70s the Imperial system has faded out in various spheres, stones are forgotten forever, miles are units used elsewhere (in the USA/UK), pounds are gone .... the fade out has been gradual. In the 90s a rugby player's vital stats read: Jim Honey - 6'2'' (188 cm), 105 kg - whereas now the even the feet and inches have gone. What the UK needs to do is complete the changeover and allow the Imperial 'fade out' to happen naturally as it does and has done here.