Young men drive faster and pay less attention to the road when they drive with their friends.
In fact, a third of all 17- to 21-year-olds admit to driving differently when they have more than one friend in the car, according to research by insurer Aviva.
The company studied young motorists' behaviour and their attitudes to driving, in an attempt to understand why young drivers are more at risk of accident or injury.
According to Department for Transport statistics, young-driver accidents and deaths are declining more slowly than in other groups of motorists.
Peer pressure to blame
The study reveals that young drivers are adversely influenced by peer pressure while driving with friends in their car.
Key findings in the report included:
• One-in-five pay less attention to the road
• A quarter admit to taking their hands off the wheel
• 15% perform illegal driving manoeuvres
• 97% drive more carefully when in the car with a parent or grandparent
Aviva carried out face-to-face interviews with young drivers to find out their experiences of driving with their friends.
Adam Gilbert, 19, from Aylesford, said: 'I think my mates drive differently with friends in their car. They are a bit more ambitious and less sensible. They might show off a little bit show how fast their car can go.'
Alex Rodwell, 17, from Barnet, said: 'I don't see the difference between putting the seatbelt over your shoulder or under your shoulder. I know if it's under it can mess up your arm and stuff and that over the shoulder is better for the impact but the belt cuts into your neck and it's uncomfortable.
'It depends on the impact because if it's side on, it does nothing.'
Aviva's Nigel Bartram said, 'Young drivers and passengers alike need to take responsibility for their own actions this means wearing a seatbelt at all times, driving with fewer passengers and not giving in to peer pressure while behind the wheel.'
Top 10 dangerous driving habits among young drivers
1 Taking hands off the wheel
=1 Shouting at other drivers
3 Turning around to talk with passengers
4 Performing illegal driving manoeuvres
5 Whistling or calling out to the opposite sex
6 Swerving the car to music on the stereo
7 Racing with other drivers
8 Jumping traffic lights
9 Overloading the car with passengers
10 Not wearing a seatbelt