WASHINGTON - Congressional Republicans plan to press Amtrak officials Tuesday on why the rail line did not move faster to install safety upgrades that could have stopped Train 188 before it derailed last month in Philadelphia.

Among the key questions expected at a morning hearing on Capitol Hill - the first since the incident that killed eight passengers - are why Amtrak did not devote more resources to activate a new-age safety system, and why an older safety system was only in place on the southbound side of the curve in Port Richmond, and not the northbound side, where the train left the tracks.

"When [lawmakers] found out that this train had actually been going over 100 m.p.h. where it should have been going much slower, I think that really sort of shocked them," said a Republican aide, who briefed reporters in advance of the hearing on the condition of anonymity.

Republicans on the House Transportation Committee also expect to ask why Amtrak had not installed inward-facing cameras that monitor engineers, and may probe why it took until early this year for Amtrak to acquire the radio spectrum needed to operate the new safety system, Positive Train Control, seven years after Congress ordered it installed.

"There is definitely a discussion on Amtrak's prioritization of funding," the GOP aide said.

The hearing may also give lawmakers a chance to press the National Transportation Safety Board on the status of its investigation, which so far has focused on the engineer operating the train, not mechanical problems.

Amtrak officials have answered some of these questions when posed by reporters, but not under the glare of lawmakers, who wage perennial battles over the rail system's value and funding.

Rail officials have said they are on pace to install Positive Train Control throughout the Northeast Corridor by the end of this year, Congress' deadline for the 2008 mandate.

Amtrak is ahead of most other rail operators when it comes to meeting that goal, but its chief executive, Joseph H. Boardman, has said more funding could have sped up the process.

The older, less sophisticated safety system - Automatic Train Control - was installed on dangerous curves after a 1990 crash in Boston. But Amtrak officials have said it was only used in areas where the approaching speed limit exceeds the speed that would cause a derailment.

That planning did not appear to account for the possibility that a train might be pushed far past the speed limit.

Train 188 was traveling over 100 m.ph., past the 80 m.p.h. speed limit approaching the Frankford Junction curve and the 50 m.ph. limit in the curve.

Under orders from the Federal Rail Administration, Amtrak installed Automatic Train Control on the northbound side of the tracks shortly after the wreck and was examining other potentially dangerous curves where it could be used along the Northeast Corridor.

Amtrak also said late last month that it would add inward-facing cameras on trains along the busy corridor. The move could let investigators see what an engineer was doing before a crash. Labor unions representing train operators have fought proposals to install the cameras.

Boardman is scheduled to testify Tuesday, along with top officials from the safety board, the Federal Rail Administration and the union for engineers.

Many Republicans have long accused Amtrak of wasting its funding, pointing to the roughly $1.4 billion a year it receives.

Democrats say the funding has been inadequate and pale in comparison to what other countries spend on rail.

"We should not be putting Amtrak in the position of having to choose between safety, like Positive Train Control and other technology, and investing in fixing crumbling bridges or crumbling infrastructure," Sen. Robert P. Casey (D., Pa.) said in May.

On Monday he wrote to senators crafting a rail bill, urging them to include added funding for Amtrak and Positive Train Control.

Rep. Ryan Costello (R., Pa.), a Transportation Committee member from Chester County, said he planned to seek answers on the status of the investigation, Amtrak's progress in implementing safety measures, and what has been done to prevent more crashes.

"I want to make sure we don't politicize the tragedy," Costello said.