according to Autoexpress they are...
http://www.autoexpress.co.uk/news/55835/passengers_pain_in_the_back_seat.html
Passengers Pain In The Back Seat
Backseat drivers aren't only annoying - they're dangerous, too. A study shows distracting passengers are to blame for one million-plus accidents and near-misses every year.
The research, by insurer Direct Line, also reveals they make a quarter of the 33.8million UK motorists drive dangerously. Panicking, providing unwanted directions and checking speed are the worst traits.
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no sh*t sherlock...
