The deadly train crash occurred just outside of Bedford on a Friday evening, leaving 53 people in the hospital, with eight in critical condition.
Investigations are underway to determine the cause of the crash, with officials stating that it is not yet possible to say what indication the driver received from the automatic warning system (AWS) equipment fitted to the train.
The AWS is designed to trigger the emergency brake unless the driver acknowledges an alert from the system, but the RAIB has yet to determine if this occurred in this incident.
Data suggests the signal behind the stationary train, which had come to a stop unexpectedly, was red. The train, which started its journey in Corby, passed this red signal, with its brakes activated for about nine seconds before the collision.
The train was travelling at approximately 76 mph and had reduced to 49 mph when the impact happened, resulting in a derailment of at least one train carriage.
Emergency responders and investigators were quickly on the scene, with patients with the most serious injuries being taken to hospital, and others receiving treatment at the scene.
One passenger, Dr. Pete Knapp, described the scene as chaotic, with people "crying" and "screaming". He said he had not felt the train slow down before the crash, but other passengers told him they had.
Dr. Knapp managed to escape the train through a gap in the doors and described seeing people with bandages and those who couldn't see straight. He said he is shaken but otherwise unharmed.
Outgoing Prime Minister Sir Keir Starmer has described the crash as "hugely concerning" and expressed gratitude to the emergency services for their swift response.
Online train trackers show the rolling stock involved in the crash was a class 360 and a class 810, with the front of the former hitting the rear of the latter. The class 810s were recently rolled out by EMR, while the class 360s are at least 20 years old.
Rail journalist Tony Miles has described the crash as a "relatively slow speed collision". Network Rail has pledged to support the efforts of emergency services and is offering its thoughts to those involved.
