Driving too close to the car in front and using mobile phones are considered the biggest threats on UK roads, a survey says.
Mobile phone-using drivers were near the top of the list, IAM said
More than half of almost 700 drivers surveyed by the Institute of Advanced Motorists (IAM) considered the two activities "highly dangerous".
Overtaking on single carriageways when there is oncoming traffic and cutting up other drivers were next on the list.
The IAM called for stiffer penalties for drivers caught using a mobile.
The IAM is an organisation working to improve UK drivers' skills.
Tailgaters topped its poll with women, with 60% of respondents naming them as a highly dangerous risk on Britain's roads, compared with only 47% of men.
Likewise, more women (61%) found talking on mobile phones while driving to be dangerous compared with men (44%).
But younger drivers were least likely to find others' activities to be dangerous.
Only 30% of those aged between 17 and 29 regarded phoning and driving to be a "highly dangerous" activity, compared with 50% in all of the other age groups of those questioned.
With tailgating, only 40% found it highly dangerous, compared with 55% in the other age groups.
Steve Norris, a former road safety minister and member of the IAM Council, said: "Many of Britain's motorists regard other drivers as lacking basic road safety skills.
"Too many road users slip into bad habits, either through ignorance, impatience or, even worse, aggression.
"Tailgating and phoning while driving are activities which are a clear threat to the safety of others. No-one has the right to drive badly but the results of bad driving fill our hospitals every day."
The IAM is urging the Highways Agency and other road safety organisations to paint more chevrons reminding people of the two-second rule - the time indicating a safe gap between two vehicles.
It also wants stiffer penalties for drivers caught using a mobile phone at the wheel, which was made illegal 18 months ago.
"More effective police action would help the government achieve the aim of making 'phoning-and-driving' as socially unacceptable as drinking-and-driving," Mr Norris said.
The survey was carried out by BRMB.