Chief financial officer Richard Burnfield said the program would be an experiment from mid-June until Labor Day.
If ridership and customer reaction is positive, SEPTA could continue the late-night service after Labor Day, Burnfield said.
SEPTA's proposed $1.33 billion operating budget and its proposed $571.8 million capital budget will be unveiled at a series of hearings starting Wednesday.
The only fare increases in the budget are the already-approved boost in cash fares that will take effect once SEPTA's long-delayed "smart card" electronic-fare system is activated.
That system is not likely to be in full use until 2015, so cash fare increases to $2.50 (from the current $2.25) that had been approved to take effect July 1 won't be imposed until the system is fully in place next year, Burnfield said.
The operating budget, up from the current $1.28 billion, includes a planned increase in the workforce from 9,440 employees to 9,526, primarily to support more construction projects.
The budget also assumes a 3 percent increase in labor costs, including wages and benefits.
SEPTA is in talks with its largest unions in an effort to avoid a possible transit strike.
The unions have asked for two annual wage increases of 5 percent, while SEPTA has offered a two-year contract with wage increases of 2 percent in the first year and 3 percent in the second.
Workers would have to spend an additional 1 percent of their wages on health-insurance premiums under the SEPTA proposal.
The proposed capital budget, which pays for major construction, new vehicles and repairs, will nearly double from the current $308 million, reflecting additional state transportation funding approved by the state legislature last November.
The new capital budget includes $117 million for new and repaired vehicles, $61 million for power substations, $58 million for communications and signal work, and $43 million for bridge repair. About $21 million will go toward the new smart-card fare system, and $95 million will go for debt and lease payments.
The hearings on the operating budget will be held in each of the five Southeastern Pennsylvania counties:
Bucks County: Wednesday, 2 and 6 p.m., Bucks County Free Library, 150 S. Pine St., Doylestown
Delaware County: April 21, 2 and 6 p.m., Delaware County Courthouse, 201 W. Front St., Media
Montgomery County: April 22, 2 and 6 p.m., Montgomery County Human Services Center, 1430 DeKalb Pike, Norristown
Philadelphia: April 23, 11 a.m. and 5 p.m., SEPTA Headquarters, Board Room, 1234 Market St.
Chester County: April 25, 2 and 6 p.m., West Chester Borough Hall, 401 E. Gay St.
Hearings on the capital budget will be April 28, at 11:30 a.m. and 5 p.m., at SEPTA headquarters.
The capital budget is available on SEPTA's website: septa.org/reports/
The operating budget will be available Wednesday at the hearing and then will be posted on the website, Burnfield said.