The smells in a car could be to blame for speeding, road rage and serious accidents, new research suggests.
Research suggests perfume can make a driver's mind wander
A study conducted by the RAC Foundation suggests that certain odours can help a driver to remain focused and recognise potential hazards quickly.
Sue Nicholson, of the RAC Foundation, said it was "astounding" how much a smell could affect a driver's actions.
A previous study by the West Virginia Wheeling Jesuit University found the smell of cinnamon aided concentration.
It also identified peppermint as an odour which had a positive effect by making drivers less irritable.
But, according to the RAC Foundation's study, the smell of camomile, jasmine and lavender could prove to be hazardous by making drivers too relaxed.
The fragrances are all used in the treatment of insomnia.
According to the study, other dangerous smells include:
Fresh cut grass - This may lead drivers to daydream about being on a country lane, prompting them to forget their speed.
Roadside flowers - Drivers who suffer from hayfever may endure streaming eyes and sneezing.
Perfumes and aftershaves - A driver's attention may wander away from the road and towards sexual thoughts.
Fast food wrappers and fresh bread - These odours could can cause irritability behind the wheel as they leave drivers feeling hungry and eager to satisfy their appetite.
And other smells that aid concentration include:
Lemon and coffee - These odours are thought to aid clear thinking.
Sea air - The bracing, salty aroma is understood to encourage deep breathing, while relaxing muscles.
'New car' smell - The combination of organic solvents and cleaning products which creates this distinctive aroma makes drivers more careful behind the wheel.
Conrad King, the RAC Foundation's consultant psychologist who carried out the research review, said: "More than any other sense, the sense of smell circumnavigates the logical part of the brain and acts on the limbic and emotional systems.
"When we bring cars into the equation, however, the ability of various smells to over or under stimulate us as drivers can have catastrophic results."
The motoring group's findings suggest that drivers tend to become de-sensitised to the smell of their cars, making them less aware of its effect on their mood.