Single hall tree
An additional problem with root pruning is the loss of tree stability.Trees have stability against wind throw because of the lateral roots.
In a 6-foot wide swale with a growing tree, that does not allow space to root prune at the edge of the sidewalk.
So root pruning should only be done as a last resort when all other methods have been judged as not feasible.
But it is too late for many people who buy a home in a development that has already planted large-maturing trees in a narrow swale between the sidewalk and the street.
This is a landscape design flaw, in my opinion, that is creating significant maintenance costs for homeowners and property managers.
Tap roots are rare and quite small in most broadleaf trees and provide virtually no support.