Next Thursday (Nov, 13) is World Usability Day. From the description:
World Usability Day was founded in 2005 as an initiative of the Usability Professionals’ Association to ensure that services and products important to human life are easier to access and simpler to use.
This year’s theme is “Transportation”, treating various aspects of usability such as interaction, signage or security. There are numerous local events across the globe picking up this theme to one degree or another. As there is no event here in Montreal, I dediced to contribute a little snapshot I took in the metro (subway) the other day. It shows the train’s emergency brake:
Before you read on, think about what would be the interaction you would take to activate the brake in case of an emergency.
For me it is not obvious. So far, I have come up with three possible interactions that I think people might want to try:
People might want to pull the brake out of the mount, away from the metal plate.
People might want to pull the brake up in a circular motion, like opening a hatch or a hinged lid.
And people might want to pull the brake down. This one might be the most common way to operate emergency brakes but to me, the short slot of about 1cm in the metal plate doesn’t suggest that the entire train would stop when pulling the brake for such a short distance.
Overall, the brake’s presentation lacks affordance, or in other words, it lacks a design that allows even first time users to immediately operate the brake in the correct manner. Why is affordance so important in this case? Emergency brakes have to respond very quickly to stop the train. In addition, I think you can assume that of all the subway passengers, practically no one has ever operated an emergency brake before, therefore making everyone a first time user. If people in an emergency now start trying different means of operating the brake, precious time is lost.