This thread reminds me of a time when I was pulling my camper through Des Moines and there was some sort of major accident on I-80 as we approached town. At the time I was in the right lane. Behind me was another camper (part of our travelling parth). Traffic was crawling along at a snails pace (so both lanes were full) and it didn't take long for some bozo to come up behind us on the shoulder at a pretty good pace. Apparently he was far more important than the rest of us safely navigating towards the scene.
Anyway, as he came up beside me he observed that the car in front of me was the Sheriff and slammed on the brakes. The Sheriff wasn't having it and gave him a very stern gesture to pull forward so he could pull in behind him. It was entertainment for us.
In Iowa the rule is to slow down and/or move over for emergency vehicles. In this case the accident wasn't actually on the road way at all but off in the ditch. The right lane was never blocked at all. We were able to stay in the lane and proceed through but many did insist on moving into the left lane which really slowed things down.