[SystemSafety] Change of passenger warnings on Hamburg subway from today.

[Karsten Loer]

Dear colleagues,

after having enjoyed the inspiring discussions on this list for several years now, mainly passively, I think I can contribute an interesting topic today:

Hochbahn, the operating company of Hamburg subway, decided that from today on the natural language warnings „zurueckbleiben bitte“ („stay clear from the train“), which used to warn passengers about closing doors of the train that is imminent to depart, will be replaced by a series of beeps.

Warnings are broadcast at the end of the stop, and are initiated by the driver after she/he has checked (by means of a set of monitors that are installed in the cockpit and/or in an area of the platform where the front of the train comes to a hold) that all doors are clear of passengers.

The old warnings, which had been in operation for several decades, consisted of a natural language message that was broadcasted via the public announcement system of the subway station. For newer train (series DT4 and DT5) this was a recording in a friendly and polite female voice, for the older DT3 train series these messages were read out by the train driver at each stop (— so as a side effect travellers were able to learn a lot about the train driver’s gender, nationality and current mood).
These warning messages were complemented by a series of short beeps at the train doors.

The new warnings are just an extended series of short beeps at the train doors. 

The justification given by Hochbahn is as follows:

Apparently, over the years some people were conditioned to interpret the old natural language warnings to stay clear of the train as a prompt to speed up an try to get into the train.

As a consequence, people would get trapped in train doors; with a potential of causing injuries to themselves and delays to the train (in the new DT4 and DT5 train series the doors will open automatically, if a certain degree of resistance is detected during the closing process; in the old DT3 trains the doors need to be opened by the train driver, if she/he becomes aware of the problem via video screen).

This causes a delay at the station. As a consequence, trains need to go faster to catch up  with the timetable. This, in turn yield an increase of power consumption which accumulates to up to 700.000€ (about 1 Million USD) per year. (Well, from personal experience asa frequent traveller on these trains, I would have thought the main concern of faster going trains would the safety of standing passengers who tend to bounce back an forth due to the higher accelerations; but that matter is not mentioned anywhere in the press statement.)

In summary, I see three arguments that are raised by the operator to justify the need for the change of warning announcements:

(1) preventing passengers from getting trapped in doors of a train that is about to leave,
(2) reducing the frequency of disturbances of the time schedule, as a consequence of (1), hence, allowing trains on route to travel at lower velocity and
(3) saving costs if operations as a consequence of (2).

As a safety analyst and concerned passenger I would like to add to this list of arguments: (4) increasing the level of comfort/reducing the potential of falls of standing passengers as a consequence of (2)


Perhaps there are other experts on this list who also doubt that changing the warnings from a combination of spoken platform announcements and audio-signals on the train to just audio-signals on the train will have the desired effect?

I wonder how long it will take for people to adapt their habits and react the door signal alone (Pavlov-effect)?

Maybe it is also worth thinking about the side conditions:
The subway trains in Hamburg operate very frequently and reliably; usually every 3-5 mins during the peak times (7am through 9pm), and every 10 mins at nighttime.
So one might wonder why people are prepared to take the risk of getting injured despite the next train arriving soon.

I wonder if people’s behavior would be likely to change if the imminent arrival of the next train would be made visible, e.g. as is done on London underground (although I am not sure if the motivation might be different). In Hamburg this information is only displayed AFTER the current train has left the platform.

Many greetings from Hamburg!

Dr. Karsten Loer

Dr. Loer system safety consulting
http://www.dr-loer.eu