Yes sure,you can find it in https://wiki.openstreetmap.org/wiki/Proposal:Extended_traffic_signs_tagging
and
https://wiki.openstreetmap.org/wiki/Key:traffic_sign

Human readable values are the most used in OSM as taginfo says so we need other tag when we want to maintain also the national id of the traffic sign. I have found the answer in taginfo,with a few items and used it.