There is NO REQUIREMENT TO MOVE OVER or slow down to a certain speed
The law states "(a) On any public roadway with at least 2 adjacent lanes proceeding in the same direction of the stationary authorized emergency vehicle, the driver of the approaching vehicle shall proceed with caution and yield the right-of-way by moving into a lane at least 1 moving lane or 2 vehicle widths apart from the stationary authorized emergency vehicle, unless directed otherwise by a police officer. If movement to an adjacent lane or 2 vehicle widths apart is not possible due to weather, road conditions, or the immediate presence of vehicular or pedestrian traffic in parallel moving lanes, the driver of the approaching vehicle shall proceed as required in subdivision (b).
(b) On any public roadway that does not have at least 2 adjacent lanes proceeding in the same direction as the stationary authorized emergency vehicle, or if the movement by the driver of the vehicle into an adjacent lane or 2 vehicle widths apart is not possible as described in subdivision (a), the approaching vehicle shall reduce and maintain a safe speed for weather, road conditions, and vehicular or pedestrian traffic and proceed with due care and caution, or as directed by a police officer."
It can be found at
http://www.legislature.mi.gov/(S(cqzdjvu3jcukyrwfkfkcuja1))/mileg.aspx?page=getObject&objectName=mcl-257-653a
Most states read the same