One of my friends was very, very ill last week and had to be taken to the hospital. His wife called the SAMU, or Service d'Aide Médicale Urgente, and asked for an ambulance. They took 45 minutes to arrive, by which time he was covered with blood. I've been told by several people here that if it's a real emergency, you should call the firemen (18), not the SAMU (15).
On the way to the hospital, the ambulance was stopped twice by policemen for using its siren and speeding! An ambulance here has right of way only when accompanied by a police escort.