Confirmed in the SR automatic I'm driving that the speedometer is consistently reading 4 km/h higher than the car's computer, which looks to me like a correction factor. I used an OBD-II scan tool (ScanGauge-e) and checked from 30-100 km/h:
Speedometer reports...
OBD-II value... 30 26 40 36 50 46 60 56 70 66 80 76 90 86 100 96
I didn't check against the odometer, but will do that too. I bet the dash display matches the OBD-II values.