Request ID: FOI-1663-2122 Date published: 08 November 2021
You asked
1. How are the tube train doors tested for functionality regarding automatically opening if there is an obstruction.
2. How regularly is the test on train doors completed on each carriage/train on the network.
3. Do drivers have the option to override the automatic opening if there is an obstruction, if so how many times in a calendar month is this done.
We answered
TfL Ref: FOI-1663-2122
Thank you for your request received by Transport for London (TfL) on 29 October 2021, asking for information about train doors.
Your request has been considered in accordance with the requirements of the Freedom of Information Act and our information access policy. I can confirm that we hold some of the information you require. You asked:
How are the tube train doors tested for functionality regarding automatically opening if there is an obstruction.
Depending on the train there are two types of door systems. The doors on the newer fleets – those which operate on the Victoria (09TS) and Metropolitan, Circle and District (S Stock) operate as follows:
09TS
The door detects an obstacle through the position encoder on the electric door operator and through monitoring the motor current
If an obstacle is detected the door will open partly and attempt to close three times with a force that is compliant to the European Standard for door impact force
After the third attempt the door will open a small amount and stay there. If someone tries to push the door open it will apply a force to stop the door from opening, but the door does not apply a squeezing force to the obstacle.
S-Stock This behaves in a similar way as the 09TS, with the following exceptions:
The S-stock door is lighter and therefore closes with a lower force
After attempting to power open three times the door will apply a force to the obstacle
Trains have door sensitive edge. The purpose of the sensitive edge is to detect a passenger being dragged as the train departs the platform after their clothing or possessions have been caught between the closed door leaves. Activation of the sensitive edge will cause the emergency brakes to apply. The sensitive edge does not operate outside of station limits. When the doors are closed and locked and an object is detected between the door seals, the Electronic Door Control Unit provides an output to the brake control.
On the older trains, the safety systems applied to the doors are as follows:
One of the technical features is the ‘pushback springs’ which allow a limited amount of door opening (approximately 100mm) to allow release of a trapped object. Every single doorway and each double doorway has one door leaf fitted with pushback springs. This means that at every doorway it is possible to push a door open by approximately 100mm, which provides enough space to release trapped garments or limbs.
Another technical feature is the ‘door interlocks’. The door interlocks are fitted to each door leaf to detect when that door leaf is in its fully closed position.
The door interlocks are connected together to provide a door proving circuit which indicates to the operator when all doors on the train are closed and electrically inhibits traction (i.e. prevents powered movement being available). The door interlock system consists of a switch mounted inside the car body, or a magnet which is mounted on the inside of the door leaf and a circuit to verify the operational state of the switch contacts. When the operator selects the “door close” push buttons, the door chimes sound, the doors then start to close and the door interlocks will return to the closed state as each door returns to the fully closed position. Once all the doors are closed, the door proving circuit becomes ‘made’ and the pilot light on the Trian Operators console will appear, indicating that the doors are fully closed and that traction can be obtained.
For the key warning feature each passenger saloon doorway is fitted with an audible sonalert (door chimes). In total the audible warning lasts for about 5 seconds. If there is an obstruction, the doors cannot close. Powered movement of the train cannot be obtained until the pilot light appears on the Train Operators console.
On the exterior of each door there is also a hazard warning label that reads ‘Keep clear of the doors’. This is to notify customers of the dangers associated with obstructing the doors.
How regularly is the test on train doors completed on each carriage/train on the network.
All rolling stock vehicles (older and newer) are subject to a maintenance plan. Different elements of the door systems are tested, inspected and maintained during daily train preparation and various other examinations.
‘Daily Train Preparation’ is performed within 24 hours prior to the train entering service, and amongst other activities verifies that the door open and close commands, door chimes, and door interlocks and traction inhibit (when doors are open) are functioning correctly.
One exam is typically performed every 28 service days and includes a Door Control inspection and test which includes checking of the door chimes.
‘Door Exam’ is performed between six monthly or annually This exam consists of an in-depth check and test of the mechanical door operating mechanisms including but not limited to the door interlocks, door pushback springs and door chimes and ensures the door systems and its safety features function correctly.
Do drivers have the option to override the automatic opening if there is an obstruction, if so how many times in a calendar month is this done.
Train Operators do have a facility to isolate the doors on the train, however, this is extremely rare and it’s not something that we record. To determine the number of instances this had happened, we would either have to ask every driver on our older trains or investigate every train’s computer or a database on our newer trains. This would be overly time consuming and exceed the ‘appropriate limit’ of £450 set by the Freedom of Information (Appropriate Limit and Fees) Regulations 2004.
Under section 12 of the FOI Act, we are not obliged to comply with a request if we estimate that the cost of determining whether we hold the information, locating and retrieving it and extracting it from other information would exceed the appropriate limit. This is calculated at £25 per hour for every hour spent on the activities described.
If this is not the information you are looking for, or if you are unable to access it for any reason, please do not hesitate to contact me.
Please see the attached information sheet for details of your right to appeal as well as information on copyright and what to do if you would like to re-use any of the information we have disclosed.
Yours sincerely
Eva Hextall FOI Case Management Team General Counsel Transport for London
