When someone's life is at stake, they should jump the traffic lights or honk to get the road clear. But they cannot do it when there is no patient inside. The drivers (of the ambulances) starts believing that it's their right to get the pass even when there is no emergency.
But that's also true that how would we know about the emergency. The ambulance, although not carrying a patient right now, might be on a run to reach the place where an accident took place just now.
In case of a doubt, I think we should do what we believe is best for everybody
"If you want to make real progress, you must give up all ideas of personal attainment".
No life without Sun
"If you are killed in action, you go to Heaven. If you win, you rule this Earth (as beautiful as Heaven). That is why, O son of Kunti, take a firm resolve and fight!"-- Shrimad Bhagwad Gita
'Idhuvum Kadandhu Pogum "
Even this challenging situation would ease