They did it here in Ireland not too long ago makes us more "european".... nobody really wanted it but dosen't take long to get used to it.....
Speed limits
30-mph became 50 km/h = faster
40-mph became 60 km/h = slower
60-mph became 100 km/h = slower
Other changes they slipped in were reduced B roads to 80 km/h and increased motorway to 120 km/h (75 mph)
They made it complusary for all new cars from jan 20th to have Km speedo only..........great for imports (from japan)
Public awareness campaign , TV , Radio, leaflets........you could probably fob off the cops at the start saying you were "confused" but not for long......Once you weren't doing 100mph in a 100km/h zone that is.....
Noticed i tend to drive a bit slower now because of Km..... before you think 60 is slow but now the needle is at 100 so Psychologically it makes me back off.....well not always but.....does have an effect
My brain is still converting to miles though.........