if you need to.... drive to the nearest ambulance station rather than the hospital - they will surely get right of way...
One thing that really saddened me was that one day there was this big entourage of some assinine bigwig of islamabad coming to Karachi - hogging the whole shahrah-e-faisal - the NICVD is also located just off shahrah-e-faisal near Regent Plaza Hotel.
At the same time one poor guy who was (as we came to know) was driving a man suffering a heart attack to the same NICVD hospital in emergency in his own car (corolla I think) was shot whilst driving because they (the security) thought he was a terrorist - they killed the patient by delaying his travel to the hospital... WHO WAS the terrorist here
as we live in a criminal society and nothing is more important than life itself - hire an ambulance at the first opportunity.