This is with reference to the current thread about over-speeding.Once while foot-plating the AK Raj,I came across this fault in the speedometer of the WAP4.It regularly crept to the limit of the dial and showed 160 kmph.Of course the drivers never exceeded the booked/max speed of 130.But still this happened.The overspeeding indicator also flashed and beeped insistently.My point is that loco speedometers are notoriously inaccurate and are prone to such defects too.Also,wheel wear and lack of regular re-calibration can affect the accuracy of the speedometers.