Acting star Joseph Fiennes is the voice of the new THINK! campaign to remind motorists of the dangers of driving when tired.
One in five of all crashes on major roads are caused by tired drivers but research shows many motorists are ignoring the simplest sign - the yawn - that it's time for a break.
Road safety minister Jim Fitzpatrick said: "We all want to finish our journeys as quickly as possible but being tired at the wheel is a proven killer.
"People who drive for work are particularly at risk but there are simple steps we can all take to make our journeys safer. Plan regular stops into a long trip and if you find yourself yawning pull over and take a break - this could make the difference between life and death."
A You Gov poll of British drivers shows only 18% of motorists always take a yawn as a sign to pull over.
Dr Neil Stanley, a sleep expert from the clinical trials and research unit at the Norfolk and Norwich University Hospital, said: "People read a yawn all wrong - they often mistake the energising effect that comes immediately after as a sign they can carry on, but tests prove this is not the case.
"Yawning quite simply means you're on the road to falling asleep - so if you're yawning behind the wheel it really is time to pull over."