Section 652. Definitions

a. The term "normal retirement age" shall mean
  age fifty-five for a member of Tier one, and age sixty-two for a  member
  of Tier two, three or four.
    b.  The  term "covered employment" shall mean paid service as a bridge
  and tunnel officer, sergeant, lieutenant, assistant  bridge  and  tunnel
  maintainer,  bridge  and  tunnel  maintainer,  senior  bridge and tunnel
  maintainer or laborer with the Triborough bridge and tunnel authority by
  a member described in section six hundred fifty of this article.
    c. The term "Tier one member" shall mean a member whose  benefits  are
  prescribed  by  chapter one of title thirteen of the administrative code
  of the city of New York and who is not  subject  to  the  provisions  of
  article eleven, fourteen or fifteen of this chapter.
    d.  The  term "Tier two member" shall mean a member whose benefits are
  prescribed by chapter one of title thirteen of the  administrative  code
  of  the city of New York and who is subject to the provisions of article
  eleven of this chapter.
    e. The term "Tier three member" shall mean a member who is subject  to
  the provisions of article fourteen of this chapter.
    f.  The  term "Tier four member" shall mean a member who is subject to
  the provisions of article fifteen of this chapter.