Having watched numerous american freight You Tube film clips, I noticed that nearly all wagons from tank cars to gondolas use the same pattern bogie (truck) including the autorack which is a low height , 3deck car carrier but has smaller wheels. This seems a sensible option especially compared to the UK where there seems to be dozens of different pattern bogie. I recall that a few years ago trying unsuccessfully to find a supplier of schlieren bogies as fitted to TEA tank wagons, which were different to those fitted to the Midland Pullman cars. Even today's wagons seem to have different pattern bogies. Is this because of higher speeds used in the UK, or because of wagon design?