By Ray Dunne
BBC News Online health staff in Llandudno
People with long-term health problems and those on regular medication could soon be ordered to stop driving.
Illness and medicines can affect a person's ability to drive
The British Medical Association is drawing up guidelines on who should be allowed to get behind the wheel of a car and who should not.
It comes amid fears that some people could be putting themselves and others at risk.
The move was announced at the British Medical Association's annual conference in Llandudno.
Doctors at the BMA are examining how various health conditions affect a person's ability to drive.
They are also looking at the impact of medicines, ranging from painkillers to powerful anti-cancer drugs.
"We are thinking directly about illnesses and indirectly about the drugs that
are used to treat illnesses," said Dr Vivienne Nathanson, its head of science and ethics.
"We are also looking at self-medication for simple illnesses like hay fever,
whether people who are taking them are fit to drive, how they can assess that
and how they can be helped to understand the law."
The advice given to patients by GPs can be taken into account in court if they are involved in a road traffic accident or other similar incident. It is an offence to drive if you are not fit to do so.
The guidelines will also look at the impact of illicit drugs, like cannabis and cocaine, on a person's ability to drive.
"We will look at how much cannabinoids affect ability to drive and how long those effects last," said Dr Nathanson.
The BMA hopes the guidelines will help GPs and other doctors to give patients better advice on when they should and should not drive.
They also hope it will encourage more people not to get behind the wheel if they have taken powerful medication or illicit drugs.
"We still need to do a great deal in terms of working with the public on changing hearts and minds in the way we succeeded with drink
driving," said Dr Nathanson.
"Thirty-five years ago I don't think people thought that drinking and driving
were incompatible; today there are very few people who would sympathise with a
friend who got into a car drunk."
The BMA is working with the Department of Transport on the issue. Dr Nathanson said the guidelines could be published later this year.
"It will be available to the public and to doctors," she said.
The AA welcomed the move.
"I think we would have to say it's a good thing," Andrew Howard, head of road safety at the AA Motoring Trust, told BBC News Online.
"Doctors should give patients advice on when they should or should not drive. They don't always do so."
But he added: "When giving that advice, they should also think about the impact it would have on a person's life. They may not be able to leave their home or work."