I was unaware of this OSM tag until today: use_sidepath. As I assume that it is currently not considered in cycling mode of Navigator, I created this feature request :-)
What it is about? In countries with compulsory cycleways (NL, DE, PL, FI), where cycleways are often mapped as separate highways, this tag is applied whenever a street should not be used by cyclists. The effect for application designers is similar to an explicit bicycle=no. Without this tag usage, Navigator in cycling mode today consideres two parallel highways, when a cycleway is running parallel another highway.
Whenever you might add this feature, please consider the table inside the above linked article ("Some more examples in which all cycleways are compulsory cycleways."): it also deals with situations, where only one direction (!) is forbidden for cyclists.