I’d like to choose my father for example. It’s about I went to the gas station with him in China last month.

The gas station looks like this picture. Normally there will be a staff help pumping gas. But sometimes the staff is too busy to help every guest.

My father is 56 years old, who is easy to forget things. “Every time I have troubles when using this self-service petrol machine.” He said to me that day. That was his 5th or 6th time of using it, but he was not used to it. I don’t know how to use it, so I just stood by and observed the process.


Firstly, I helped to buy a ticket from service shop, which has a bar code on it. I just told the clerks how much money I’ll pay and which fuel grade.

( My assumptions of the next processes are: scan the bar code, a signal will tell me to start, then remove the nozzle from the pump and put it in the tank, and pump gas, when it’s shut off, put it back.)

Secondly, my father put the ticket in a scan box. There was a red line showing the scan process.


He waited for a while, nothing happened. The meter didn’t change at all, which only showed number zero. He didn’t know what’s going on, so he asked the staff for help. The staff just pushed the button next to the scan box, then the gas meter began to change, showing the amount of money of the ticket.



Thirdly, he took off the nozzle, opened the lid of gas tank, put the cap down, plug the nozzle in it, then pressed the handle on the gas nozzle to start pumping, but still nothing happened. We both felt helpless and anxious, because there were a lot of cars waiting in line behind us.


My father checked around the gas machine and the car back and forth, finally he realized that he forgot to lift the gas pump’s lever up. The lever was where the nozzle was.


Fourthly, he put the gas cap back on and closed the gas tank.

Finally, he put the gas pump back in its holster. The lever  lower down automatically.

The whole transaction took about 10 minutes.



The difficulties part is how to start. There are two procedures go beyond my assumption, which are exactly where my father got stuck.: press the confirm button beside the scan box and lift the gas pump’s lever up. However, the core process of pumping gas appears to be the easiest part and takes the least amount of time. It takes about 6 or more minutes for beginners like us to do preparation work.

My father is doing physical interaction with the self-service petrol machine. Pressing a confirm button triggers the process of “thinking”. Scanning the bar code is the process of input. Telling us information through meter is a kind of response. Lifting the gas pump’s lever up is another input to trigger the process of “thinking”. Then the machine reads the pressing on the handle of the gas nozzle as input, takes actions of filling gas as output. At last, putting the gas pump back is the input message of stop “thinking”.

During my father’s operation, the feedback system performed too bad. There should be feedback when the scan box read the bar code at the first time, even though the user didn’t press the button. The machine should tell users what’s wrong with it and how to revise the operation. What’s more, the design of lifting the gas pump’s lever up before pumping is not a natural way. Users have to think about it for a while, this is something that can easily stump users. The operation makes no sense for who’re not used to it, and there’re also no response of the mistake. So users tend to forget the process, and beginers like me have to learn from others in order to proceed.

By contrast, by pressing the handle on the gas nozzle to start pumping is more natural. Users use one hand to hold the nozzle, the handle is just in the position where users’ fingers are. And its movement direction is the same with the hand’s direction of force. So it’s easy to use, and without thinking. I love this design very much.