State Transportation Commissioner Vance Smith is facing more questions from board members over the Department of Transportation’s thin top management ranks.

Smith’s latest move was to fill one of the key divisions of the department with somebody already doing double duty.

To replace the retiring head of the DOT’s high-profile, high-stakes program to build billion-dollar toll roads, Smith tapped Chief Engineer Gerald Ross. Ross, who is already filling in as a deputy commissioner, will now direct the toll road program — called the Public-Private Partnership, or P3, program — thus continuing to fill two or three of the department’s top jobs. Ross will continue as deputy commissioner until someone is hired for that position. DOT spokesman David Spear said the position will be filled “reasonably soon.”

Within the department, the P3 job is one of the most important. The program is putting out to bid the state’s first-ever public-private toll road, along I-75 and I-575 in Cherokee and Cobb counties, estimated to cost about $1 billion. Georgia has never done such a project before, has spent years working through stumbles and is on the verge of its climactic moment: evaluating bids.

Some board members expressed continuing frustration that Smith had not filled out the DOT’s top management.

“I knew [Ross] had his plate loaded as chief engineer; now he’s got this,” P3 committee member Jay Shaw said. “I don’t know how he’s going to balance all of it, but we’ll see.”

Committee member Jeff Lewis said he wanted to know whether Ross will fill the P3 position permanently or if it’s an interim measure. Lewis and all board members interviewed hastened to say the decision was up to Smith.

Shaw, other members of the board’s P3 committee and Board Chairman Rudy Bowen said that they learned about Ross’ appointment only after receiving an email notification Tuesday, the day it was announced. The committee’s chairman, Brandon Beach, said Smith had told him about it the day before.

The staffing problems, particularly the lack of a permanent deputy commissioner, came to a head in May after the then-treasurer, Kate Pfirman, announced her resignation. Her deputy stepped in to fill those duties and has now been made treasurer.

Board member Sam Wellborn said Wednesday that the treasurer pick was a good decision, and that he supported Smith. Some other board members this week declined to answer whether they supported retaining Smith as commissioner.

A majority of the DOT board’s 13 members hire and fire the commissioner, who manages a budget of about $2 billion and leads the 4,600 employees who run the state’s road system.

After a closed-door meeting about the personnel issues in May, Bowen said he was confident Smith would hire a new deputy commissioner. Wednesday, more than three months later, Bowen said Smith had a short list of candidates and “we’re working on that.”

Bowen would not comment on his feelings about Smith’s progress, he said, until after he had talked to Smith and to the board, which he hoped to do within a week or so.

The I-75/I-575 toll project has weathered several delays. The DOT recently said it intended to bid out the project Aug. 29. It has now been rescheduled, according to the DOT, in order to allow the boards of three state agencies to weigh in first on Sept. 15.

Ross replaces Sandra Burgess, who is retiring this week, according to a DOT statement. Ross has been with the department about three decades. Asked whether Ross had retirement plans of his own, a DOT spokesman did not respond.