Relationship between the displayed speed and the actual speed
According to the national standard "speedometer for automobiles" (GB15082-2008), the speedometer indicates that the speed of the vehicle must not be lower than the actual speed.
Considering the tolerance errors on the speedometer, in order to prevent speeding, we manufacturers usually make the displayed speed higher than actual speed.
But meanwhile, the following relationship should be satisfied between the displayed speed and the actual speed:
1. Displayed speed ≥ Actual speed
2. Displayed speed ≤ Actual sped + Actual speed/10 + 4km/h