Layoffs could follow, and officials would not say how many of the 2,250 employees are expected to lose their jobs.
"It's just not a pleasant time for anybody in the private sector or the government sector," turnpike chief executive Joe Brimmeier said Thursday. "Times are tough."
The turnpike has instituted other cost-saving measures, including reductions in gasoline use, efforts to make vehicles last longer and cutbacks on printing and copying. Brimmeier said his goal is an immediate savings of $10 million, with more to come later.
He said the commission would not reduce its level of service and would continue a $500 million-a-year capital improvement effort.
Brimmeier said traffic volume on the toll road system fell by 1.6 percent during the June-September period compared with the same period last year, and the commission is projecting a 4.4 percent revenue shortfall for the current fiscal year.
Brimmeier attributed the problem to high gas prices and a drop in discretionary travel brought on by the slumping economy.
"We're going to see how many people will take advantage of this incentive program and then go from there," said turnpike spokesman Carl DeFebo. "If you're going to get serious about cutting costs, you have to look at payroll."
Any resignations under the program will become effective Nov. 20.
Chuck Ardo, a spokesman to Gov. Ed Rendell, said the moves did not come as a surprise to the administration, which itself is grappling with a massive budget shortfall.
"We'll have to wait and see what transpires, but clearly the turnpike needs to make the same kind of decisions that other governmental and non-governmental entities have to make," Ardo said.
House Minority Leader Sam Smith, R-Jefferson, said the turnpike's money problems raised questions about its borrowing - indebtedness driven partly by a 2007 transportation bill that also established a now-stalled proposal to add tolls to Interstate 80.
"I have significant concerns that the turnpike commission is digging themselves into a deeper financial hole," Smith said.
Brimmeier's letter said the lower traffic levels and the commission's belt-tightening were not expected to affect the agency's ability to provide $1.3 billion in new transportation funding through May 2010. Turnpike tolls are scheduled to increase by 25 percent in January and by smaller amounts in subsequent years.
Phone messages were not immediately returned Thursday from Teamsters union officials who represent nonmanagement turnpike employees, primarily toll collectors and maintenance workers.
The turnpike system's 359-mile main stem runs from the Delaware River to the Ohio line; it also includes a 110-mile northeastern extension from Philadelphia to Scranton as well as western expansions. The turnpike served 185 million vehicles in 2007.