Of course, modern vehicles are extremely complicated pieces of equipment, and sometimes new technologies catch operators by surprise. Such is the case with recent emissions equipment designed to reduce the amount of harmful pollutants emitted by diesel engines, as they have the power to bring the vehicle to a grinding halt if not properly serviced.
A grinding halt is exactly what one ambulance in the Washington, DC area came to recently while carrying a 34-year-old man to the hospital. According to Firefighters Union President Ed Smith, a four-level warning system should have let operators know the ambulance was low on diesel exhaust fluid (read: urea), but the system apparently did not function as designed. The US Environmental Protection Agency does not require emergency vehicles to be equipped with engine shutdown systems, according to this PDF, but it would appear some ambulances have not been retrofitted with the proper modifications to keep them running.
Sadly, the critically injured patient died at the hospital. The ambulance had come to a stop on a highway, and a second ambulance had to be dispatched to pick up the man being transported, adding between five and seven minutes to his trip to the hospital. The incident is currently being investigated. Click here to read more about diesel exhaust fluid and its role in reducing emissions, and scroll down below to watch a video report from WUSA9, a local news station.