"The safety of our passengers and crew remains our No. 1 priority," said Amtrak president and CEO Joe Boardman Sunday, in a written statement. "Our infrastructure repairs have been made with the utmost care and emphasis on infrastructure integrity, including complete compliance with Federal Railroad Administration directives."
The first train will roll out of Philadelphia at 5:53 am and New York City at 5:30 am. Amtrak says all Acela Express, Northeast Regional and other services will also resume.
The National Transportation Safety Board's investigation into last Tuesday's accident continues. The NTSB is tapping FBI experts to investigate whether a mark on the windshield of Amtrak Northeast Regional Train 188 was made by a hurled projectile -- or even a bullet -- before it derailed in Philadelphia last week.
"The FBI will be on the scene (Monday) to assist us to identify what that may have been," NTSB board member Robert Sumwalt told CNN's "State of the Union" on Sunday.
At least two other trains -- a regional Southeastern Pennsylvania Transportation Authority train and an Amtrak Acela -- reported being struck with projectiles in the area near the crash site.
SEPTA passenger Alfred Price told CNN he heard a loud boom before the train he was riding on came to a stop, and the engineer, who appeared shaken, told passengers something had hit the train. A photo of the front of the SEPTA train shows a circular crack on the windshield.
Kam Desai was a passenger on the Acela that was about 20 minutes ahead of Train 188 when something struck and cracked the side window on the row behind her. "We heard a very large, really loud slamming or banging sound," Desai said. "It was very alarming to all the passengers, myself included, and my co-worker that was with me."
Sumwalt said last week the assistant conductor of the doomed Amtrak train told investigators that she overheard engineer Brandon Bostian say in a radio transmission that their train had been struck by something.
But Sumwalt seemed to cast doubt on that account Sunday when he told CNN that he had listened to all of the radio disptaches from all trains in that area that night and that "there was nothing, nothing at all from (Bostian) to dispatch to say that his train had been struck. Furthermore we interviewed the SEPTA engineer and he did not recall having any conversation (with Bostian)."
"Nevertheless," he told CNN's Brianna Keilar, "we have the mark on the windshield of the Amtrak train, so we certainly want to trace that lead down."
New safety measures ordered
Meanwhile, Amtrak spent the weekend installing new speed controls on the curved section of track at Frankford Junction where the fatal derailment occurred, the result of an order by the Federal Railroad Administration to install the Automatic Train Control system as an immediate step to improve safety.
ATC has been in place throughout the Northeast Corridor, the most heavily traveled rail network in the country, for nearly 40 years. The system notifies an engineer if a train is speeding and applies the brakes automatically if the engineer does not respond.
The system is in place at Frankford Junction for southbound trains, which enter the 50-mph curve from a maximum speed of 110 mph, Amtrak says. But it's not in place for northbound trains, which enter from a maximum speed of 80 mph.
Amtrak 188 was traveling northbound at 106 mph when it entered the curve, causing it it to careen off the tracks so violently that three of the seven cars that derailed were left standing upright.
"Had the train been operating at max authorized speed heading into the curve, it would not have come off the tracks," Amtrak wrote.
As for why the speed controls weren't installed on the northbound tracks in the first place, Amtrak said it came down to the"risk envelope."
"The rationale behind the decision not to install there (which was made in the 1990s) is that the drop in speed (from 80 to 50) is considered within the risk envelope," Amtrak explained to CNN via email. "Going the other way, the decrease in speed is much greater going into the curve (110 to 50), so that's why ATC was installed there."
The FRA also instructed Amtrak to assess the risk of all curves on the corridor where the approach speed is significantly higher than curve speed, and to increase speed limit signage throughout the corridor.
Amtrak said it would immediately implement the measures.
Acting FRA administrator Sarah Feinberg said that these measures must be taken before Northeast Corridor service is resumed at full capacity, which Amtrak hopes to do by Monday or Tuesday, according to Feinberg.
Better speed controls by year's end
Amtrak is in the process of installing a sharper technology known as Positive Train Control on all of its tracks. The PTC system is already in service between Boston and New Haven, Connecticut, but is in service on only 50 of the 226 miles of track between Washington and New York.
It is not installed at Frankford Junction.
PTC is a programmable system that uses transponders in the tracks to communicate with computers on locomotives. As a train passes over a transponder, it switches the train's onboard radio to the proper channel and helps the train receive the appropriate information about speed restrictions and routes, according to Amtrak.
As with ATC, the system sends a warning to the engineer if the train is speeding and applies the brakes if the engineer doesn't respond.
Congress ordered the nation's railroads to adopt PTC by December 2015 in response to a head-on collision that killed 25 people in 2008 near Los Angeles. The technology is complicated and expensive, but Amtrak says it is on schedule to meet the end-of-year deadline.
Sumwalt and Amtrak Chief Executive Joseph Boardman said the derailment would not have happened if PTC had been in place.