How to move through lists with a large number of items.

Context

Operators need to find entries in lists, which have more entries than can be displayed on one screen.

Forces

With too many entries to scroll through, scrollbars become inefficient.

Solution

Explicit solution via control

The scrollbar control is usually fine for lists, that are approximately double the length of the visible display area, i.e., two pages. Longer lists need other mechanisms to reduce their length, for example, a quick search control. The up and down buttons are placed on the bottom of the scrollbar, which prevents the user’s hand from covering the list content.

Sample

Implicit solution via direct manipulation

Other solutions as seen in gesture-based computers like the iPad and the iPhone do not necessarily provide explicit controls for scrolling but rather offer direct manipulation. In these interfaces, lists are controlled via inertial scrolling, which reduces the amount of friction considerably.

Usability impact

Using this pattern may increase efficiency when working with list, however, it must be used with care as it does not work well for long lists.

Safety impact

Long lists requiring scrolling should be avoided from a safety point of view, so using scroll bars is a compromise.

Especially devices that are rarely used in a safety-relevant context should use explicit controls, as infrequent users may not remember how to use implicit (e.g., inertial) scrolling in critical situations.