When I was driving over the road (I'm retired now). I was Northbound I-5 in Milton, WA. I was in the slow lane of 5 Northbound lanes. A ambulance was Northbound in the car pool lanes (extreme left lane) with his emergency lights on, doing around 70 MPH with no traffic in front of him. A car in front of me see's the ambulances emergency lights and decides to come to a complete stop (he didn't pull over to the shoulder) in the slow lane. I was driving a set of doubles (35' & 28' trailers) and all I could see was the back window of this car when I can to a skidding stop! I didn't hit this car but was 6" from his back bumper. Talk about idiots driving cars!