COLUMBIA - The director of South Carolina's transportation department resigned Friday following a drunken-driving arrest.

Robert St. Onge resigned, effective immediately, citing personal reasons, in a letter obtained by The Associated Press. Gov. Nikki Haley notified legislative leaders in a separate letter that Christy Hall, deputy secretary of finance, will be acting secretary until she finds a permanent replacement.

"General St. Onge is a good man with a lifetime of service to his country, and more recently, our state. That said, we have a no-tolerance policy for our state agency directors, and so General St. Onge has resigned as secretary of transportation," said Haley spokesman Doug Mayer. "The governor thanks him for his work fixing the serious fiscal issues he inherited at the Department of Transportation - the state is better off because of his service."

Highway Patrol Sgt. Bob Beres said St. Onge was stopped about 8 a.m. Friday on Interstate 20, near the intersection with Interstate 26. After failing a roadside sobriety test, St. Onge was arrested and taken to the Lexington County jail, where a breath test registered his blood-alcohol level at 0.20 percent, Beres said. That's more than twice the legal threshold of 0.08 percent.

The sheriff's department says St. Onge was released from jail Friday afternoon on his own recognizance.

No one answered the phone Friday at his home, and messages were not immediately returned. It was unclear if St. Onge had an attorney.

Haley named the retired Army major general to lead the transportation department in January 2011, saying she wanted someone in the position whose decisions could not be bought or swayed. The 66-year-old Lexington resident retired in 2003 after 34 years in the Army. From 2001 to 2003, he was the deputy assistant secretary of defense for reserve affairs. His previous posts include commanding general of the 24th infantry division at Fort Riley in Kansas, policy director for the Army's chief of staff and commandant at West Point. Before joining Haley's administration, he was an executive at defense contractor L-3 Communications.

St. Onge has often said his job is to "manage the decline of the state highway system." He had to strike a balance between asking legislators for more money to fix South Carolina's roads without suggesting where the money should come from, as Haley has repeatedly vowed to veto any bill that increases the state's 16-cents-per-gallon gas tax, unchanged since 1987.

According to the Department of Transportation, the state needs an additional $1.5 billion yearly over the next 20 years just to bring roads and bridges to good condition. A law passed last year could generate up to $1 billion over a decade for roadwork, through a combination of state and federal money plus borrowing.

St. Onge has said he welcomes any bit of money to repair the system.

He actually had two bosses: Haley and the DOT commission. A 2007 law restructuring the agency put it in the governor's Cabinet and gave oversight to a board elected by legislators. Haley has asked legislators to eliminate the commission, saying the entire department shouldn't answer to two bosses. But that effort died.