[NevadaWolf]

The key is being safe and being seen. There are times when the center of the road is the safest. There are times when you avoid it like the plague. Typically, because of the bump and the sludge that accumulates there, its not a good idea to remain in that position.

The only reference to the center position i could find in the RMV manual was this passage:

Lane Sharing
It is recommended that motorcycle riders avoid sharing lanes with other vehicles. All motor vehicles are permitted to use the full lane of travel to ensure safe operation. Motorcycle riders are prohibited from riding alongside motor vehicles within a marked travel lane. Position the cycle in the center of the travel lane to discourage motorists from attempting to squeeze by the cycle. Motorists are more prone to this type of behavior when traveling in heavy traffic, passing vehicles, turning, and entering or exiting highways. Further, a responsible rider recognizes the potential for injury and avoids traveling between rows of stopped motor vehicles.

Being in the left position accomplishes the same since it blocks a vehicle from cutting between you and the center line. This is the reason the right position on a two lane road isn't normally safe since cars will do this to you.