Originally Posted by abhibeckert

A friend on a nice tandem with a speedometer measured how fast I can go on blades once... With a smooth concrete footpath I was able to maintain about 40km/h for a few minutes (and then we reached a section with not-so-smooth concrete and had to slow down).

And I don't even have proper high speed skates. I've heard of people hitting 100km/h down steep hills.

With good bearings/wheels, it's possible to get a lot of speed on these things - especially if you know how line them up just right (at those speeds, the slightest angle will send you face first into the ground).