Dean Dorricott thought his car's speedometer reading was 5km/h too slow. So he compensated by speeding up. It seems he was wrong. Last December, the Whangarei electrician drove past two roadside indicators at Onerahi. They suggested he was travelling at 45km/h, when his speedo read 50km/h.


Quote from the article:

Mr Dorricott, 59, thought this meant his car's speedometer was inaccurate by 5km/h. Until he got a speeding ticket. Mr Dorricott is challenging the ticket, and says the roadside indicator put him wrong. He had been towing an empty trailer on State Highway One at Ruakaka. The speed limit for cars towing trailers is 90km/h. "My speedometer indicated 100km/h and considering the error on my speedo I should have been driving at 90km/h. He was stopped by police who said he had been travelling at 103km/h.

Source: When all else fails, blame roadside speed indicators