Yes there is. It is quite normal to represent a long path as several 'ways' joined end to end, so that different tags may be attached to different sections of the path.
Create nodes at the points where the access restriction changes, if there are not nodes there already. Then split the way at those two points. You now have three ways joined together, where there used to be just one. The acces access restriction can then be changed as necessary for each section of the path.
In Potlatch 2, a new node is added to a way using shift and left-click at the point where the node is wanted, and the way may then be split at that point using the 'scissors' icon.