I did some statistics over whole OSM with help of osmium. Restriction types are NO (no_right/left/U/straight) only (only_right/left/straight), no exit/entry and unknown where it wasn't possible to figure out restriction.
Script only reads relations with type=restriction and which have restriction tag. This includes most of restrictions but skips
transport specific ones like type=restriction:hgv
, type=restriction:motorcar
and restriction:hgv=only_right_turn
.
I found 574 028 restrictions with type=restriction and some restriction. Out of this 17 098 are invalid. Some don't have from/to ways, or just one of them some have multiple from/to ways where only one is permitted (except no exit/entry)