Motorists waste the equivalent of 29 hours every year using sat navs, according to a new study.

The time is lost when the devices send drivers either the long way or wrong way to their destinations, the report commissioned by black cab app mytaxi found.

The figure is based on analysis of the proportion of journeys delayed by sat nav misdirection and the average length of the hold-ups.

A poll of 2,000 drivers revealed that 27% cite confusing directions as the most annoying aspect of sat navs.