First of all, I think the upcoming switch from MPH to KPH is a minor one. I don't think drivers should have any real trouble with the conversion. The first two cars I owned here had only KPH on the speedometer. Took about 2 minutes to figure it out.
I can't, however, understand why some speeds were ignored. I had hoped that when we moved to metric some of the speed limits would be raised slightly. There are a lot of roads in S. Dublin with a 40 MPH limit. The N11 Stillorgan Road is one example. I had figured that when the metric limits were introduced, the limit would go to 70 KPH (about 43 MPH). But, it seems that 70 KPH limits will not exist. Nor will 90 KPH. Why?
All roads that currently have a 40 MPH limit will be slowed down to 60 KPH (around 37 MPH). Similarly, there are some roads for which 80 KPH will be too slow and 100 too fast. Why not 90?
Somewhat related is the whole issue of signs. I can't understand why we don't use HUGE signs with the speed limits in both KPH (big numbering) and MPH (small numbering) displayed. I've always thought that the little red circle signs that are used to let motorists know that they've entered a new speed limit zone were inadequate. Speed limits should be in every driver's face. It's too easy to miss those small signs.
But, most of all, I've been wondering, why are we bothering? What benefit do we get by switching? Why is the state going to this expense? Will it mean that new cars here will cost more because we'll be out of whack with the UK? I see no good reason for this change.
