• rishinthomas

How steering law can increase usability?

Did you even hear about the steering law? Is that something law related to car steering?


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Steering Law predicts the time necessary to steer a pointer (such as a mouse cursor) through a bounded tunnel (such as a menu, a scroll bar, or slider). The steering time depends on the length and the width of the tunnel: the longer and the narrower the tunnel, the more time will be required to successfully steer through it (NNgroup). The equation for calculating the time is


The equation for calculating the time

Don’t be irritated. I know none of us have no interest to use the equation. I am not going to explain or derive this equation. :D


Try it yourself: hold your arm out directly in front of you and move your hand from left to right. You’ll notice that, even if you attempt to keep it moving in a straight line, your arm will always have a subtle arc in the movement. As a result, using one’s hand to move in a long, straight line is physically difficult.

Taking WINDOWS as an example, we can easily know the difference between the horizontal movement of the hand(left to right)and the vertical movement of the hand(top to bottom) and how much it affects the interaction cost. We can see this by taking the start screen of both windows 7 windows 10.

  1. Windows 7 start screen without applying steering law.



Windows 7 start screen

In windows 7 when a user clicks on the start button, it will show menu options. When the user clicks on the required menu, it will show the submenu options horizontally downward. Interaction cost is high for choosing the submenu options that are horizontally downwards. It is because we can’t achieve our target easily by moving the mouse cursor horizontally

We can feel this difficulty by using a horizontal opening menu bar.


2. Windows 10 start screen with steering law.


windows 10 start screen

In windows 10 when a user clicks on the start button, it will show menu options. When the user clicks on the required menu, it will show the submenu option vertically downwards. Interaction cost is less for choosing the submenu options that are vertically downwards. It is because we can achieve our target easily by moving the mouse cursor vertically downwards.

We can feel this easiness by using a windows 10 start screen or any vertically downward opening menu.


Did anyone frustrate by the closing of the submenu bar again and again?


When a user opens the submenu bar in a horizontal downward direction, they will jump directly to the required option to speed up their task. But the submenu option closes always and they have to open it again and again. This is a common problem faced by the number of users.


But if we redesign that submenu option to vertically downward, we can easily achieve our task because of the vertical downward movement of our hand. Thereby we can decrease the interaction cost.


The closing of the submenu again and again happens due to the horizontal movement of our hand using the mouse cursor. By applying vertical movement, we can solve this and users can decrease the time for achieving the task. Thereby we can decrease the interaction cost and increase usability.


Reference:nngroup

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