As a result, the last piece of Interstate 90 will not open to motorists until mid-January at the earliest, officials said. The roadway, which connects to the Ted Williams Tunnel, was originally scheduled to open in December 2001, then Sept. 7 of this year, then Nov. 8, and then Dec. 20.

But while the delay is just the latest in a series of setbacks for frustrated motorists, project officials said yesterday that it would not hurt taxpayer wallets.

The delay will translate into a loss of $33.4 million if the opening takes place as late as Jan. 26, but the project's contingency reserves will cover the new costs without adding to the Central Artery's $14.6 billion price tag, said Big Dig spokesman Sean O'Neill.

He added that the opening will probably occur one or two weeks before Jan. 26 anyway, but declined to specify a date.

The project's current financial statements, released last month, show the contingency funds for this piece of the Big Dig running out on Jan. 8. But O'Neill said that the project's private-sector managers, Bechtel/Parsons Brinckerhoff, reevaluated and updated the contingency information recently, scraping together a few extra weeks of financial cushion.

"This is why you put together a conservative contingency," O'Neill said. "We're getting down to very minute software issues here, and there's bound to be problems."

State Representative Joseph Sullivan, the Braintree Democrat who chairs the House Transportation Committee, said the problems should concern taxpayers because they could signal a new round of cost hikes. Sullivan has frequently asked the Big Dig to protect the contingency as a give-back to the public, but Bechtel officials have told the committee that the money will probably be consumed by the project.

"It should be alarming to the people of Massachusetts that this type of delay, delay, delay has triggered, in the past, additional expenditure that is borne by the state," Sullivan said.

He noted that state officials promised in the 1980s that the federal government would pick up 80 percent of the Big Dig's total cost. Now the figure will end up closer to 50 percent, with the state paying the balance.

If the I-90 opening does not take place before Jan. 26, when the newly expanded contingency fund runs out, the state will be left with the bill, he said.

"This kind of cost increase was never part of the original equation," Sullivan said.

Boston Fire Commissioner Paul Christian said he will meet today with project officials for a briefing on the fire system's problems. He said his office has worked side-by-side with Big Dig officials to understand the radio, fire suppression, and alarm systems.

But Christian also said that his department, which must certify the fire system before the tunnels can open, cannot begin its work until the Big Dig's contractor, Honeywell Technology Solutions, has ironed out the current problems. He said he had "no idea" how long it will take the Boston Fire Department to certify the systems once Honeywell has prepared them for inspection.

The problems are not entirely Honeywell's, however. Project officials have acknowledged that Honeywell has not gained access to some parts of the tunnel system to install equipment and cables because other work needs to be completed first.

A recent tour of the project showed that some areas opened to Honeywell are missing floors and feature different dimensions than their plans had portrayed. But those problems are not related to the alarm glitches, officials say.

Honeywell, which was awarded the job of creating the Big Dig's "Integrated Project Control System," has seen its $104 million contract rise by nearly $50 million since beginning its work in 1999. State officials paid out some of that money as an incentive for Honeywell to meet schedule dates, and they now say the project may demand the return of those funds.

It was unclear yesterday how the latest round of delays will affect the rest of the Big Dig's tunnel openings. In the past, project officials have said they would need about one month after the I-90 opening to cut the ribbon on the project's next milestone, the northbound side of the Interstate 93 artery tunnels beneath downtown Boston, and the northbound lanes of the Leonard P. Zakim Bunker Hill Bridge.

After that, they expect a year to elapse before some southbound tunnels would open.

Last month, Turnpike Chairman Matthew Amorello promised Democratic Party officials that the project would be "98 percent complete" when the party's national convention kicks off on July 26, 2004.