The lack of toilets on the Elizabeth line has been blamed for passengers attempting to force open train doors, leaving them stranded outside Paddington station for up to five hours.
Four trains on the Lizzie Line, two Heathrow Express trains and a Great Western Railways intercity service came to a standstill at around 6.45pm on December 7 last year when Network Rail overhead power cables near Ladbroke Grove were damaged.
A report by the rail watchdog and a passenger action group on Thursday found that passengers on both the Elizabeth line and the Heathrow Express faced a "frustrating and chaotic experience" as they waited for help until almost 11pm that evening.
It said the lack of toilets on the Elizabeth line - there are none on the £1bn fleet of nine carriages - appeared to be a "contributing factor" to passengers self-evacuating.
The Office of Rail and Road and Transport Focus report said: "All affected train services were busy and the factors affecting passenger comfort varied between operators.
GWR and Heathrow Express passengers had toilets and charging facilities on board, which passengers were initially able to use during the incident.
"The Elizabeth Line, on the other hand, is not equipped with such facilities - which later turned out to be a contributing factor to the self-evacuation of passengers.
"In addition, passengers on both the GWR and Heathrow Express initially had access to refreshments (mainly bottled water), while passengers on the Elizabeth line did not."
There were reports at the time that passengers had to urinate on seats. The GWR was extra busy as it was the penultimate long-distance service from Paddington that day due to an overtime ban by Aslef.
Network Rail CEO Andrew Haines was one of the GWR passengers and later apologised to the thousands of passengers who had been 'let down' by the rail industry.
The report says more attention should be paid to the welfare of passengers on stranded trains, and suggests that a dedicated staff member be appointed as a 'stranded train champion' in such incidents.
This revealed that more than once a day a train was stuck on the British rail network, being stuck between stations for at least two hours.
The report said the incident on 7 December meant that power was cut to all lines between Paddington and Maidenhead. It said the "volume of passengers affected was significant and the overall situation serious".
The report said: "During the incident, GWR and Heathrow Express passengers were frustrated that their journeys had been delayed, although the general atmosphere in the carriages remained friendly. Interviewees said people were in 'good spirits'.
"On the Elizabeth line the situation was exactly the opposite: there was no air conditioning, no toilets and no charging facilities (and there was also less light). Some stranded passengers started to behave badly and tried to force the doors open.
"One passenger noted that there were announcements saying 'can people stop trying to open the emergency doors to get out (...), can people stop kicking the doors - I know you're frustrated but please stop doing that'. This further exacerbated the already stressful and unpleasant atmosphere on the train."
The report said a Heathrow Express staff member told passengers they would be evacuated at 8.45pm, 15 minutes before the doors opened.
This prompted passengers to get ready, "resulting in the carriages becoming more crowded and making it more difficult for staff to move and warn remaining passengers".
The information then had to be distributed verbally to passengers. In addition, stranded passengers were not given any information about evacuation or safety procedures. However, they were assisted by the fire brigade in getting out and walking along the track towards Hanwell station.
On the Elizabeth Line, British Transport Police (BTP) began evacuating stranded passengers at around 10.30pm.
However, some passengers were unsure whether it was an official evacuation or a passenger-led evacuation. There were no official announcements and the "self-evacuations" had already begun.
The report said: "Many passengers decided to jump out, which was riskier than if BTP had instructed them to do, and join the crowd for a 'fairly dangerous walk' to the next station.
"At the start of the evacuation, passengers were directed towards Paddington for approximately 5-10 minutes but were then told to turn around and go the other way, which caused further physical and mental strain.
"Once at the station, passengers were advised to find their own transport home, which was difficult for many whose phones were dead. The fact that it was dark added to their anxiety, especially for female passengers."
One female passenger told investigators: "I was literally left in a place in London that I didn't know, completely alone as a woman, and my battery was almost dead. (...) I was panicking about how I was going to get home."
Passengers were not advised on how to claim compensation for their onward journey, the report said.
Passengers on the GWR and Heathrow Express trains reported that as the incident progressed, the toilet facilities reached a state where they were no longer hygienic.
One passenger said: "The toilets were pretty bad, there was no way to flush them. Everyone was there trying to flush and it wasn't working, for me the toilet was completely inaccessible."
People were also unable to wash their hands, something one passenger cited as a major problem in the post-pandemic era.
The report also examines three other incidents involving stranded trains in December, including one on December 21 at Bourne End Junction near Hemel Hempstead on the West Coast Main Line.
It was reported that during the 70-day investigation period (October 30 to January 8), 75 incidents occurred, resulting in 178 trains being stranded. In 20 cases, passengers had to be evacuated.
On average, there was just over one incident per day, usually involving at least two trains.
Of the 20 evacuated trains, in five cases passengers had to walk along the tracks to a station and in six cases, all related to the same incident, the situation was considered 'out of control'. Passengers took matters into their own hands and climbed out of the trains.
The report states: "In summary, in addition to efforts to reduce the number of stranded trains, effective management of the incidents that do occur is vital to ensure passenger safety, wellbeing and the customer experience."
Stephanie Tobyn, director of strategy at ORR, said: "Fortunately, it is rare for people to be stuck on a train for an extended period of time, but when it does happen, train operators and Network Rail must work together quickly to assess the situation from the passenger perspective and create a workable plan to manage the situation safely.
"This plan should assess the conditions on the train, the specific welfare needs of all passengers on board and previous experiences of the public's behaviour during such incidents.
"It is clear from conversations with passengers that staff have done their utmost in very difficult circumstances. Rail companies and Network Rail must improve training and preparedness to implement established procedures so they can mobilise more quickly to provide effective assistance to passengers on board the train and, should evacuation be necessary, to help them complete their journey."
Natasha Grice, director at Transport Focus, said: "Passengers can reasonably expect the rail industry to respond more quickly and effectively to stranded train situations. The railways' responsibility for passengers does not end when they finally disembark from a stranded train. The industry must up its game to ensure passengers are well looked after even after they have been rescued, including onward travel and hotels where necessary."
