Sat nav driving motorists round the bend

Satellite navigation systems designed to help motorists avoid jams are instead driving them around the bend with defective directions, says a report by consumer magazine Which?.

Demand for systems has soared and an estimated one in eight (12 per cent) of Britain's 32 million drivers already have one fitted in their car – equivalent to nearly four million devices.

But the watchdog says too many sat nav systems are "fallible and unreliable" . Two out of 14 devices it tested sent drivers down dirt tracks; another nearly caused an accident when it told the driver to skirt a queue by performing a dangerous U-turn.

The test follows a spate of incidents in which drivers have been directed sent into rivers or flooded fords. In the Which? tests, Garmin's Nuvi 300 sent one tester down a gated farm track in Northumberland before eventually emerging on a main road.

Magellan's Roadmate 800 took another researcher down a rutted dirt road near Eastleigh, Hants, whilst on another occasion it directed him into a dead end in the National Trust's Petworth Park estate in West Sussex.

In the evaluations to assess navigation accuracy, ease of use and features, the Nuvi 300 came out top with 88 per cent followed by TomTom's GO 910 and the Becker Cascade 7944 – both on 86 per cent.

Which? also said that those devices which have access to live traffic updates are supposed to warn of jams ahead. But usually they alert subscribers only to "exceptional" hold-ups caused by accidents or roadworks.

They can be blind to jams on roads where congestion is "endemic".

The consumer magazine warned motorists that they should be careful about relying on these devices and a sat nav system is "not a magic wand" .

Senior researcher George Marshall-Thornhill said: "These devices are fallible and can be unreliable. As a blind navigation aid, they are limited so don't rely on them completely or you could end up down a blind alley.

They don't have intuition and are only as good as the information they are programmed with."