Why the hell have two buttons on a train door in the first place? #cabb

Buttons beside a train door

Half asleep, with my mind numbed and elsewhere by a monotonous commute, I find myself looking like a complete numpty as I hammer the closed button to open the train door. With 20-30 people waiting to get off behind me, someone reaches over my shoulder and presses the open button. There was a collective sigh from the other passengers that confirmed my status as the first moron of the day: maybe even an early contender for plonker de jour.

There was little recovery from this embarrassment BUT like any good HCI and interaction designer I have tried to find a way of blaming the design rather than me, the user. How could you improve such a simple system? Surely there’s no way you can get out of being such an idiot here?

Well, I think I have an answer: why the hell have two buttons on a train door in the first place? Surely just one button would do, and it would do better: push to open when it is shut, and push to shut when it is open. If you can think of a good reason to have two buttons please tell me because I can’t think of one.

Whilst you ponder that also ponder my new design for a light switch (picture below). The left switch turns on the light, and the right switch turns off the light. Neat eh?

This blog was brought to you by CABB: Campaign Against Bad Buttons. See the video Why Buttons Go Bad. We think the world should be full of better buttons and less idiots.
N.B. Mistakes such as these are shared on www.errordiary.org

8 responses to this post.

  1. For one, stereotypes. Would people intuitively know you needed to press the button to open/close? Probably… But this is a well known stereotype. (lift doors)

    I reckon you could solve the problem with much less retrofitting cost by color coding the buttons.


    • With regard to stereotypes I could say “Just because we have done things wrong for ages doesn’t mean we should continue,” but I think that is going too far. Established stereotypes and metaphors need to be considered in interaction design but i don’t buy it for this case. I have just noticed they have one button on the outside of the door as I suggest and two buttons inside – if stereotype was that important why not two on the outside?

      Incidentally I was on a more dated train not too long ago that only had one button on the inside too. I think one button makes the interaction easier and it halves the amount of buttons to buy, fit and maintain.

      In terms of disambiguation between the buttons and their salience this is already high as the correct button to press lights up. Salience and disambiguation often help with slip errors but it’s surely better to design the confusion/error out of the interaction in the first place. There’ll be a great example of the limitations of salience in my next post (another example of a bad button – probably my favourite – The Magic Belsize Button).

      The train door issue isn’t significant enough an issue to consider a retrofit, I raise it more to get people thinking about interaction design and to convey to users, “It’s not your fault.”

      The only reason I can think for having two buttons on the inside would be to privilege controls to those inside the train e.g. if they wanted to keep someone threatening off they could hold the close button. However, I don’t think this is the case.


  2. Posted by Sarah Wiseman on September 18, 2012 at 10:45 am

    I think the two buttons may be necessary for those on the inside, as they represent two actions that users may want to complete, regardless of door state.

    I understand the close button, when it’s cold and the train is waiting in a station I want to be able to put as many layers between me and the outside as possible. In this situation, the one button option you suggest would work.

    However, I have just rushed on to a train as I hear the beeping noise of imminent door closure. But I have noticed someone behind me trying to get on the train too, just as the doors close. If I want to be a polite commuting citizen, I want to be able to press the open button *whilst* the doors are open to ensure they stay that way. Sure the person the outside could press the open button on the outside of the door, but what if they have their hands full or are in a rush, or haven’t noticed the doors closing in the first place. I want to be able to hold a door open for them!

    Changing it to one button would be cost effective, and probably sensible in most situations. But it just isn’t polite, Dom. Where are your manners?


  3. Good points Sarah. Holding doors open for fellow commuters isn’t something that springs to mind after you have been living in London a while – not serious of course ;). Some thoughts…

    If the train is about to leave, and the doors are going to shut, I don’t think the open button does anything. The priority is the train leaving and so the doors will close unless you put an arm or leg in the way.

    There are instances on more modern trains that don’t yet need to leave but where open doors will beep and close automatically if they have been open too long – the open button works here and arguably that is a justification for having two buttons. I think this is quite a good justification. However, doors behaving in this was are only a recent thing in my experience e.g. 3 or 4 years, before they just stayed open until the train was ready to leave if they were opened. So, I believe, there were plenty of two button designs around without the doors behaving in this manner. Is there still some rationale that we haven’t thought of?

    BTW one button could have lights that changed from in green (open), to >< in red (close). This could then work in the door shutting early scenario, i.e. as it beeps and is shutting the button lights go to green to invite you to press it if you still want it open. If the train is about to pull away it shouldn’t light at all if it doesn’t do anything anyway. I think that is polite enough.


  4. Posted by Andrew on November 1, 2012 at 7:46 am

    It’s for those on the inside.

    My local station is the terminus, so I generally get on the train 10 minutes before it leaves. Good etiquette is that you open the door, get on, and close the door behind you. Just like in all situations in life: you close the door behind you. But INFURIATINGLY people open the door and waltz on and leave everyone freezing cold.

    The answer is to have an auto closing door that’s timed and one button to open it. Although really this just adds to the problem – people expect everything to be automated. So they don’t even think to close a door they just opened!! This didn’t happen with slam door trains.


  5. Posted by An Annoyed Person to has to move here..... on January 13, 2013 at 10:51 pm

    its not a freaking elevator…. its stupid to have buttons… get a conductor that opens the doors… learn from NYC. Then I heard the trains dont stop at the stations by themself.. WTF IS THAT? how is someone supposed to get on, if no one wants to get off.. -___-


    • It is not completely pointless. At busy city centre stations (e.g. City Thameslink) it may slightly speed up service for all the doors to open automatically. However, trains that stop at City Thameslink may also continue on to Shoreham, by which time there won’t be many people on the train & only a few people will get off. It is a waste of energy to open every single door in the entire train.
      Request stops: The train only stops if a passenger has requested or if the driver sees people standing on the platform looking at the train. People usually wave their hands to prevent the driver from not noticing them. This system is usually used on local railway lines which connect a minor city to small villages with people who work there, or on railway lines which go through sparsely populated areas in Wales or Scotland. These lines tend to be single track, which is unusual for a British railway.


  6. Good post, Dom!

    My 2 cents: The door can only have 2 states: open or closed (ignoring the momentary ‘in transit’ state for now). For that reason, it makes sense to have a design that reflects that: a simple toggle button.

    In 20 years of commuting I don’t think I’ve ever seen anyone hold an automatic door open in the way described above. (But that might be a reflection of SWT passengers 🙂
    The point is, do the buttons actually work that way anyway, i.e. if they are in the momentary ‘in transit’ state, does pressing the open button cancel a close action?

    If it doesn’t then all the politeness in the world isn’t going to make this design a good one.


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