The S2s deployed in Oxford are showing a significant (2.5% to 5%) “long tail” of high speeds (43+ mph, 70+ km/hr), even the ones on 20mph streets, some in locations with significant traffic calming. Because these are a relatively small fraction of measurements, it seems possible that they are (mostly) the result of some kind of systematic error.
See for example the measurements here 9000005087 and the Google Streeview shows the quite aggressive tables at either end of the segment - and (not shown on Streetview) there is now a modal filter (bollard) at the eastern end, so cars are have to turn to enter the segment: Google Maps I’m not convinced 4% of cars are getting up to 40+ mph here.