> Miles are great to estimate time of travel by car, take 1 minute per mile of distance on a highway and 2 minutes in the city and you will be pretty close.

That might be true where you live, but it's hardly a universal constant. 1 minute per mile might be sort-of-universal for long distance Interstate driving, but then again, you can just as easily phrase that as ~1 hour per 100 km in metric.

I'm rather doubtful about your 2 minutes per mile (= 30 mph average speed) figure for "city" driving, though – how's that even possible when urban maximum speeds are usually in the 25 – 40 mph range, and that's not counting time lost for traffic lights and other intersections, general congestion and parking?

Checking a few destinations around where I live in Germany, non-Autobahn cross-country driving is closer to 2 minutes per mile rather than 1 minute per mile (and highly variable depending on your exact destination, so no point trying to estimate driving times to the nearest minute, anyway), and never mind actual urban driving.