A female driver who tailgated an ambulance through rush-hour traffic told gardai who stopped her that it was her cousin in the back of the ambulance.
Sharon McDonagh (24) then received a garda escort to James Connolly Memorial Hospital, but admitted at the hospital gates she didn't know the person in the ambulance.
She was trying to avoid rush-hour traffic.
Judge David McHugh fined McDonagh €100, but she avoided a driving ban.
Garda Ciaran Geraghty said he was on mobile patrol and stopped in heavy traffic when he saw an ambulance, with its sirens and flashing lights, overtaking traffic.
Gda Geraghty said a Ford Transit van was tailgating the ambulance.
Gda Geraghty said McDonagh overtook at least 40 stationary cars.
He stopped the van and spoke to McDonagh, who told him her cousin was in the ambulance.
Gda Geraghty then provided a garda escort to McDonagh, at a safe speed, to the hospital.
He said she flashed him at the entrance to the hospital and admitted she didn't know the person in the ambulance.
Solicitor Simon Fleming claimed it was McDonagh's husband, who was a passenger in the car, who told Gda Geraghty the defendant's cousin was in the ambulance.
Gda Geraghty disputed this, saying the defendant said it to him.
Mr Fleming said McDonagh accepted she had made a mistake.
He said McDonagh has no children, but needs her driving licence as she helps to bring her nieces and nephews to school.
The defendant, of Cappagh Road in Finglas, admitted before Blanchardstown District Court to careless driving at Snugboro Road Extension, Dublin 15 just before 4pm on January 9.
Judge McHugh said he would not ban McDonagh from driving.