To successfully pass the mission, get to the accident site within posted time limit, escort ambulance to hospital within posted time limit. To earn a commendation, get the ambulance to the hospital within 2 minutes. Keep your eye on the ambulance to make sure that he's keeping up with you - if it gets too far away, he'll just stop and wait for you to return. Also, make sure that when you make turns to slow down more than normal -the ambulance can't turn corners as fast as your squad car.