Jim Holt asks:

What percentage of the ambulances that blare their sirens to go through red lights are actually carrying patients? Less than 50 percent based on my observations of ambulances arriving at St. Vincent’s Hospital in Greenwich Village. And in no case have I seen the ambulance driver behave with any urgency in getting a patient out of the vehicle and into the hospital upon arrival. So is there any point to the ambulance sirens that are always deafening pedestrians and pulling down the quality of New York street life?