For the movement of loads on overweight permits, often there will be a speed/position designations on the bridge that will require traffic control whiel the load crosses the bridge. Note that for some low risk bridges, they do not require active traffic control using a load pilot. For other bridges all other traffis may need to be stopped either side of the bridge while the overweight load/vehicle crosses. 

The requirements are listed on the overweight permit, and the good practice procedures used are contained in the industry document:

Download Good Practice Guide for Traffic Control at Bridges Being Crossed by Overweight Vehicles