Ralentir belong to the 2nd
group. Ralentir is a common french verb.
Ralentir is conjugated the same way that verbs that end in : -ir
Ralentir is conjugated with auxiliary avoir
Ralentir verb is
direct transitive, intransitive.
French verb ralentir can be conjugated in the reflexive form: Se ralentir
verb is a direct transitive verb, so passive voice can be used.