Retired bank executive Don Horner has been reappointed to the Honolulu Authority for Rapid Transportation’s board of directors by Mayor Kirk Caldwell.

Currently vice chairman of the HART board, he has been a board member for four years. His new, five-year term begins next month.

The 11-member, voluntary and unpaid HART board oversees the city’s $6 billion rail project, the most expensive public works project in the state’s history.

Caldwell, in a release, cited Horner’s financial background as important for the board “as HART contends with controlling expenses in this environment of rising construction costs.”

By law, the mayor appoints three people to the board, the City Council appoints three others and the HART board itself appoints a member. Three others are automatic appointments — the state transportation director, the city transportation services director and the city planning and permitting director. Only the DPP director is a non-voting member.

The HART board is in the midst of a series of roster changes. Earlier this month, Caldwell appointed former Congresswoman to the board, replacing Carrie Okinaga. Last week, the Council voted to appoint attorney Terrance Lee, replacing board Finance Chairman Keslie Hui.

HART appointee Robert Bunda announced recently that he will be stepping down at the end of this month. The HART board is issuing a call for nominations next month to replace him.