With sleek commuter trains out of the picture for now, the Triangle Transit Authority is laboring to meet demand for more transit service with a creaking fleet of buses that are hobbled by spooky electrical glitches and chronic mechanical maladies.

Repair costs are climbing as TTA puts more miles -- a record 2.75 million miles last year -- on 63 buses that serve 4,000 daily riders with suburban links between Research Triangle Park and the Triangle's city bus lines.

Commuters are pushing for more frequent runs on crowded TTA express buses that connect Raleigh with Durham and Chapel Hill. Local mayors are clamoring for new routes for workers and students from Pittsboro, Wake Forest, Clayton and other outlying towns.

But expanded service requires additional buses that cost more than $300,000 apiece. TTA may find it difficult in the coming year to simply keep its aging fleet at current strength.

More than half its buses -- 18 full-size coaches and TTA's entire fleet of 19 shuttles -- are scheduled for retirement in 2008. David D. King, TTA's general manager, wants $12.5 million to buy 37 heavy-duty replacement buses built to last 12 years. But so far, he has pinpointed likely federal money -- which transit agencies typically rely on for 80 percent of bus replacement costs -- for only 10 or 11 new buses.

"That's a reality check on any grandiose plans anybody might have for bus expansion," King said.

Cities file suits

Most of TTA's maintenance headaches involve 44 transit coaches made by Thomas Built Buses, a High Point manufacturer better known for school buses.

Raleigh and Greensboro transit agencies have called these Thomas buses lemons.

The city of Raleigh wants Thomas Built to take back 15 buses that Raleigh bought for $2.8 million in 2000 and 2001. The city filed suit against Thomas in December in Wake Superior Court.

The lawsuit cites 615 warranty repairs to its Thomas buses for electrical, engine and mechanical faults. During the warranty period -- one to three years, depending on which part of the vehicle is involved -- Raleigh's Capital Area Transit had to tow these 15 buses to the garage 123 times for repairs that kept them out of service for days or weeks, according to the lawsuit.

Greensboro bought eight Thomas coaches in 1999 and said, in a 2001 lawsuit, that it had to take them out of service 525 times in two years for warranty repairs. Greensboro dropped its suit in 2003 after Thomas promised to make electrical and brake repairs.

Thomas spokesman Allen Haggai did not return calls seeking comment.

TTA officials cite similar problems. But they say they are using the Thomas buses harder than was ever expected in 1998, when TTA bought its first batch of 20.

"We started out small," said Laurie Barrett, bus operations director. "We grew. The buses were suitable for the time, and then our service demands changed. We really do need a heavy-duty bus, and that's what we intend to purchase."

Record of repairs

The federal government classified the Thomas buses as medium-duty vehicles that should be good for 10 years. King worries that repair costs will rise sharply for buses that stay on the road longer than that.

But records at TTA's overflowing maintenance garage suggest that newer Thomas models are just as likely as the 1998 buses to return for repairs as often as once or twice a week.

Bus 2104, a 2002 model, put 51,873 miles on the road and made 76 trips to the maintenance shop in 2006, at a cost of $20,308.53. Some of the work was for preventive maintenance, new tires and routine repair.

Work orders for Bus 2104 also list a few dozen complaints for electrical and mechanical ills that are common across TTA's fleet of Thomas coaches. They include faulty heat and air-conditioning, doors that don't close or don't open, and malfunctioning lights, fare boxes, radios and signals.

TTA says it spent $1.65 million during fiscal 2006, which ended June 30, on maintenance labor and repairs. That averages out to more than $26,000 for each bus and shuttle.

"Head lights will only work on bright, even then go out at times," one driver wrote on a Jan. 26 inspection report for a 1998 vintage bus. "Rear side doors will open and close all by themselves."

That bus spent six hours in the shop Jan. 31. It returned to the shop for two hours the next day, to fix the heat.

"We have had electrical problems with these buses, I guess, from day one," said Ed Evans, TTA maintenance superintendent.

Summer months are the worst for bus breakdowns that can leave commuters stranded and steaming on the roadside. Last July, TTA sent out 38 fresh replacements for disabled buses that could not finish their routes.

On a couple of hot afternoons last August, TTA's standing-room-only express bus from Raleigh to Chapel Hill broke down on Interstate 40.

"One time it took a very long time for them to come to get us," recalled Joal Hall Broun, who works in the N.C. Secretary of State's office. "The other time it was fairly quickly."

Roy G. Campbell of Carrboro, a fellow TTA commuter who works at the N.C. Museum of Natural Sciences in Raleigh, said the I-40 breakdowns left some riders unwilling to trust the transit agency.

"They felt it was not dependable," Campbell said. "It was undermining their confidence in the system."

Riders pile on

When TTA began buying its Thomas coach fleet in 1998, it was planning a regional transit network to be centered on commuter trains running near N.C. 147 and I-40 from Durham to RTP, Cary and Raleigh.

TTA shelved its $810 million rail project last year after the Federal Transit Administration doubted it would serve enough riders to warrant the cost. Triangle planners, elected officials and residents will update the region's transit priorities this year. TTA may be asked to revive its rail project or to develop new plans in other corridors.

Meanwhile, Triangle bus agencies report steady ridership gains. TTA's passenger count grew by 17 percent in the first nine months of 2006. Citing the increased demand, Triangle mayors have asked TTA and city transit agencies to make recommendations for expanded regional bus service.

King said he will focus first on finding money to maintain reliable service on existing routes. He wants federal permission to replace some of the old buses with money earmarked for the rail project.

"We've got to grow ridership to improve mobility in the Triangle, and you can't do that with sorry equipment," King said.

One expansion project is moving ahead. TTA is enlarging its maintenance garage near Research Triangle Park, where all six repair bays stay busy and there are usually a few more buses waiting for attention.

When the construction is finished in December, TTA mechanics will be able to fix 10 buses at a time.