I'm not convinced this is operator error. This is the first run on this route so it's unlikely the engineer was asleep.

2nd Hand copy paste from another part of the web I visit. I couldn't find the original source:

"If the wheels locked up at 81.1 MPH on the 1.4% down grade there would be no way to slow that lightweight train as in 41 seconds it would be into the 30 MPH curve. The engineer would not have time to release the locked-up brakes, apply sand and make a new braking application. Even with electronic brakes, the system does not work that fast. The NTSB should not take a year, like happened regarding the engineer who failed to stop at Hoboken, had failed to blow his horn at many crossing in his trip and the Conductor failed to check on his bad performance during that inbound train trip. That NJ Transit train had an inward facing camera but its recording was kept secret for over a year.
This was a passenger only track and the rail conditions were not likely felt by the engineer as there were no prior locations where he could get a feel of the slipperiness of the rail head. This was a new line and even thought there were many qualifying test trips, it could be likely this was the first morning with just the right dampness, temperature to make very bad rail conditions. Were many test runs made at this early time of morning?
As far back in the 1960, when single Budd Rail Diesel Cars were use on commuter runs with various station stops in an early Fall morning, some morning the rails were so slimy the RDC’s Rollacon anti-slide system would release the brakes when the wheels locked up, and the RDC would fail to stop at the platform and have to back up. One morning this happened at 3stations so when the engineer approached the terminal interlocking with a possible red signal, there was a very slow approach as going past a red signal could not be corrected by a short back up.
Many East Coast electrified commuter railroads are very familiar with bad rail condition caused by ground up leaves on the rail head which creates carbon black and misty water for a very efficient lubricant that can only be eliminated with sand. But electric suburban cars do not have sand. There is an entire industry used to wash the rail head and apply solutions to improve the traction for these trains
Railfans who own and use their own track motor cars (Speeders) become well qualified of the need to test for the rail conditions and learn the distance it would take to stop at any place on their run. A leaf ground-up track can be so slimy that a light track car can fail to get enough traction to go up a 0.10 % grade without spinning their power wheel. You cannot even gain any speed as the wheels will just spin out. And if you’re coming down a 1 or 2% grade, with is very common on many lines, you can go into a slide and wish you had an anchor to throw out. Being on a frozen rail track, and then have some very misty or rain situation, can be worst that being on a highway that was frozen over and then have been rain on over the ice. Sometimes in those cases a car rubber tire will just coast you over to the curb with just the crown on the street. Most cases a rail head can be worse than any highway surface for having traction.
I believe the train 501 wheels locked up and the train slid into the 30 MPH curve at too high a speed.
PS: Positive Train Control will not know of the possible bad rail condition and this wreck may have happened regardless of PTC in effect or not. That system cannot tell which is the worst case rail condition and is designed for the average expectation of conditions. So much for crewless trains, that will never happen. "