Although my numbers stand corrected I think my point stands unblemished. The hour is too long a period to measure something as instantaneous as speed. The old imperial units were designed to keep the numbers relevant to the scale of the measurand. Metric falls down spectacularly on this. Although it turns out that millimetres are the ideal unit to measure a length of wood when you're cutting it, and kilometres are prob ok when you get used to them, when getting down to precision engineering the micron turns out to be uselessly small, but the 'thou' (1/1000 inch) is exactly the right size. Scale mattered before the computerisation of the world, now it's an irrelevance. I think we lost something there.