Usability case study: The NYC subway turnstiles

This week I went out for an observational study about the interaction between people and the NYC subway turnstiles.

NYU subway turnstile
NYU subway turnstile

The study was made on two busy subway stations: Bedford Avenue station in Brooklyn, and Union Square station in Manhattan. The observations, and the conclusions, were similar on both stations. Therefore, I will specify my findings in an unanimous form.

Findings

  1. A few meters before they get to the turnstiles, people reach to their pockets, wallets, or bags to get a paper card, shaped as a credit card. One face of the card is painted in yellow, and the other one is painted white.
    It is very unusual to see people get to the machine empty handed.

    Getting the cards in advance
    Getting the cards in advance
  2. People swipe the card on the right side of the machine.

    Swiping the metro cards
    Swiping the metro cards
  3. Usually, a ‘click’ sound is heard after the swipe, and the ‘swiper’ moves across the gate to enter the subway platform.
  4. Occasionally, a ‘beep’ sound was heard after people swiped their cards. After the ‘beep’, people were seen swiping their cards again. This scenario repeats itself until the ‘click’ sound was heard, after which, the swiper entered the platform.
    A closer look shows an ‘error’ message on the small display, placed just above the card swiping deck.

    Errors
    Errors
  5. On rare occasions, the swiper was swiping the card, a ‘beep’ sound was heard, and the swiper seemed angry.
    This situation made other people, who were lined-up behind the swiper, angry as well. A few of the waiting people were trying to move to another turnstile line.
    The swiper turned back, and went to the ‘refill machine’. After doing so, the swiper repeated the steps from step 2.
  6. The turnstile was used, by different people, both for entering the platform, and exiting from it.
    On many occasions, people were trying to exit the platform from a turnstile that was occupied by other people, who where trying to enter the platform.
    Ofter 1-2 second of confusion, the ‘exitter’ (it was never the one who enters) was turning to another turnstile to exit the platform. Some of the exitters took the liberty of exitting the platform from the emergency exit, which was open at all times.

    Commuters go in and out the platform through the turnstile, or through the emergency exit door
    Commuters go in and out the platform through the turnstile, or through the emergency exit door

Major insights

  1. The NYC subway turnstile is a very understandable device. Whether it is because people tend to use it often, of because its design is very simple, people rarely get confused while using it.
  2. At first sight, it felt like the the fact that people use the same turnstile to enter and to exit the platform indicates a design flaw, that might become a major one on rush hours. A longer observation on the turnstiles reveal that people tend to work-around this limitation pretty easily, while spending about a second or two doing so.
  3. Since there is no indication on the card for the amount of funds attached to it, people tend to block the turnstile on cases of ‘insufficient funds’, and to repeat previous steps in the interaction.

Conclusions

Be careful of over-engineering – Intuitively, I was surprised that the engineers, who designed the turnstile, were not concerned by the fact that people would have to cross the turnstile from both of its sides at the same time (to enter and to exit the platform). I assumed that a better design was one that allowed entering and exiting the platform from different locations.
But engineering and design are all about decision making, and compromises. The design I thought about is one that requires more space, and eventually less effective. Apparently, people do not care that much about this ‘limitation’, and address it very easily.
There might be an optimal design that could solve this situation, but sometimes, looking for complex solutions for simple situation is just over-engineering.

An indication for the amount of funds on the cards could be helpful – Since people tend to hold their subway (metro) cards a few steps before they reach the turnstile, having an indication for the amount of funds on the card could save time and frustration when addressing a situation of ‘insufficient funds’.
Also, it could have been useful if people were able to fill their cards with ‘rides’, instead of plain money. For example, one would be able to fill a card with 1-10 rides, instead of $20-$60. This situation could make it easier for people to track and remember the number of rides they still have in their credit (currently, the cost per ride is $2.75, which make it relatively hard to calculate the number of rides in $20, and supposably leads to ignorance).
Here are few suggestions for such indications on the NYC metro card:
Suggestion for NYC metro card design