The organisation wants a "traffic light" system, with red, amber or green markings indicating whether it is safe to drive after taking a medicine.
The findings indicated that 3m drivers think taking aspirin and then driving can be dangerous, when it is not.
But another 3m drivers think it is safe to drive after taking a product such as Night Nurse, though warnings on the packet say it is not.
Edmund King, executive director of the RAC Foundation, told the BBC: "There is total confusion out there.
"That is why we want a much clearer labelling system. We are in favour of this traffic light system, whereby if there is a red mark on the packet you really should not drive, if it is amber you should read the instructions or take advice and if it is green, it should not affect you."
Lives at risk
The Conservative Party is backing the scheme. "Millions of motorists are putting their lives at risk, and the lives of others, by taking certain medicines and then driving," said shadow health secretary Liam Fox.
The RAC says 20m drivers will take to the roads over the Bank Holiday weekend and 5m of the could be driving unsafely.
It highlights hayfever drugs as a particular problem - where data exists, it is estimated that antihistamines are involved in 2% of fatal road accidents.
Mr King said many people only need the drugs for short time each year and so are not aware of the drowsiness they can cause.
"With the traffic light system, every time the motorist picks up the drugs, they would see if it was safe to drive."
Rather than saying motorists could not drive, they should be encouraged to use other drugs which do not have an affect, he said.
Of the 498 motorists surveyed in the NOP/MotorBus poll, 70% said they thought a traffic light-style warning system on drugs packs would be useful.