Tag:maxspeed=implicit

maxspeed = 
Description
Used for traffic signs that remove previous maxspeed restrictions Show/edit corresponding data item.
Group: restrictions
Used on these elements
may be used on nodesmay be used on waysmay be used on areas (and multipolygon relations)should not be used on relations (except multipolygon relations)
See also
Status: in use

From a quick survey it appears the tag maxspeed= is used in combination with traffic_sign=maxspeed for traffic signs that remove previous maxspeed restrictions. The tag introduction was maybe done by pictures and descriptions on traffic_sign=* main page see chapter Key:traffic_sign#Editor_support.

See also