Lea Lane used to be an obscure single carriageway running through the village of Bradpole in Dorset. It’s known to locals as the route that King Charles took when fleeing Cromwell’s Roundheads 400 years ago and until recently has been used by no more than a few local drivers going about their daily business.

Today it is a teeming thoroughfare for commuters. Traffic jams are common and villagers must regularly contend with articulated lorries getting stuck down the narrow road. It is a transformation that is being mirrored on roads throughout the country and the reason for it is simple: sat nav.

In-car satellite navigation systems were supposed to make motorists’ lives easier and journeys quicker. Instead they are being blamed for creating a new network of rat runs by directing drivers down obscure roads and ancient rights of way to cut journey times.

While some drivers, blindly following instructions, have found themselves cursing the gadgets for taking them onto impenetrable dirt tracks, down one-way streets and even into farmyards, it has also left local residents infuriated.

“It’s ridiculous,” says Simon Williams, chairman of a local residents’ association in Bradpole. “They are sticking these things in salesmen’s cars, delivery vans and lorries. They don’t know the road and if you follow them they are an absolute nuisance.”

Bradpole is not alone: unwitting victims of sat nav are springing up across the country. Among the sufferers is Chris Hayter, owner of Bond’s Lawn Farm in the once-quiet village of Haccombe, Devon. “We now get lorries, vans and cars up here all the time. They follow their sat nav directions from Newton Abbot to Torquay and it takes them right through my farm,” he says.

The problem is particularly bad in rural areas. Residents of Barrow Gurney, Somerset, have accused sat nav manufacturers of turning their village into a “car park” in less than a year, with more than 10,000 vehicles a day now using it as a rat run to Bristol airport. Traffic levels are so bad that officials at North Somerset council are trying to get the route taken off digital maps.

Residents of the once sleepy village of Birch Green in Essex are up in arms over the sudden popularity of a private track that leads nowhere. Drivers directed down the road by their sat navs are forced to backtrack through the village. The track hasn’t been a through road since the 1800s and until recently the only traffic using it was farm tractors and weekend anglers.

Sat nav systems rely on a global positioning device that receives signals from a network of American satellites to track a car’s movements. Drivers punch in their location and destination at the start of a journey and the quickest route is plotted on a screen. An automated voice can provide instructions throughout the trip.

The most basic systems rely solely on a digital road map stored on a memory card or CD-Rom that has to be periodically updated to take account of changes in road layout. The most advanced can also alert motorists to congestion hotspots and provide alternative routes to avoid snarl-ups.

The actual road mapping is provided by commercial companies that use Ordnance Survey information. Because virtually every road in the country is mapped, regardless of usage, little-used lanes or shortcuts previously known only to locals can just as easily be plotted as routes as the usual signposted roads.

Ordnance Survey, which provides road mapping for Tele Atlas, a commercial company that in turn sells the information on to sat nav manufactures, says that the roads it maps are given detailed weightings on a scale of 1-6 (1 being a motorway and 6 being an unclassified road). This weighting doesn’t always prevent drivers being sent the wrong way.

“There is the potential that drivers will get routed down smaller roads because the mathematical calculation always shows which route is the shortest journey even if they are unclassified roads,” says Gavin Jackman, senior product manager at Ordnance Survey.

The problem has been intensified by the booming popularity of sat nav. More than 2.2m vehicles now have the system, according to a government estimate. A fifth of new cars have the devices fitted as standard, although the majority of units are bought off the shelf in shops such as Halfords or Dixons and can cost as little as £200. Navigation software can be downloaded onto a PDA or smart phone for a fraction of that. Portable sat navs were one of the most popular gifts at Christmas.

Take-up has been so rapid that more than 250,000 sat nav systems were sold in the third quarter of last year, compared with just over 67,000 systems in the first quarter, according to the National Criminal Intelligence Service, which monitors the trade in sat navs because they are a new source of crime. Police blame the devices for a sharp increase in car break-ins as opportunist thieves smash windows and steal the systems.

Theft and being directed down a cul-de-sac are not the only problems. Privilege Insurance claims that one in 10 drivers use the controls of their sat nav while driving, requiring them to take their eyes off the road for an average of 10 seconds. Several lorries are also thought to have crashed into railway bridges because sat nav devices failed to point out their low height, according to Network Rail, the infrastructure company.

TomTom, the biggest seller of sat nav systems in the UK, admits that “thousands” of roads have out of date or inadequate mapping and that it receives 100 complaints a week from drivers who have been sent the wrong way. It is working with motorists and independent mapping companies to remedy the problem.

For some drivers this can’t come soon enough. Stewart Lockhart, an ambulance service employee from Alexandria, near Dumbarton, who has installed a £400 TomTom system in his car, has discovered that his increased reliance on the technology has meant he has fallen foul of the law.

“I have committed a lot of traffic offences because of my sat nav,” he says. “It often tells me to go the wrong way down one-way streets in Paisley. It tells me to take right-hand turns when it is illegal and it sends me down bus and taxi lanes. I bought it to make my life easier, but it is useless.”

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