Black boxes: Can you trust them to lower your car insurance?
Young drivers trying to save money on insurance by fitting monitoring devices to their car could be being failed, it has emerged.
Black boxes are supposed to use GPS to monitor 'good' and 'bad' driving.
But an investigation by the BBC's Watchdog programme indicates they could be recording false results.
Insurers involved in the investigation acknowledged the errors but said they were confident in their black box policies.
Black boxes monitor drivers' every move to give a "score" to insurers, which could lower the premium if they are classed as "good".
If people are monitored speeding, braking suddenly and accelerating, or even driving at night, they can be classed as a bad driver, which could put the price up or cause the policy to be cancelled.
But some drivers have raised some serious suspicions about the results they have been given.
Eva Jonas, 18, from Cornwall, was shocked when Autosaint cancelled her £1,332 insurance policy after her black box caught her allegedly driving at 119 mph on a B road during rush hour.
"It was just ridiculous," she said. "They acted as if I was driving some kind of sports car when in fact I was driving my 2001 Skoda Fabia, which couldn't even go to 119 mph."
When a professional racing driver tested the speed of the 15-year-old car, he found it could not get over 80 mph on a road the same distance.
After she had already bought a new policy, Ms Jonas did receive an apology from Autosaint, which said it believed a GPS interference error was to blame for the speeding result.
The company said it compensated her to cover the difference of an alternative premium and added that it is constantly reviewing its process to make sure this does not happen again.
Concerns were also raised when 18-year-old Abigail Sykes, from Doncaster, apparently took the box out of her car and left it on the kitchen table for four days - but later found it had continued to record safe driving.
One Call Insurance said it recorded four car journeys after her father Davan Sykes cancelled the policy.
It said the agreement permits collection of data for up to three months from policy cancellation, but it has removed these scored from the system at Mr Syke's request.
Shannan Hibbins, 18, from Lancashire, reported problems when her More Than black box recorded her driving non-stop for five days without stopping.
More Than said it was a "rare and unusual event", but apologised to Ms Hibbins, replaced her black box and compensated her with £230.
Watchdog is broadcast on BBC One at 20:00 GMT on Wednesdays. You can also watch afterwards on BBC iPlayer.