Understanding Motion Actuation

Intent

The intent of this success criterion is to ensure that functions that are triggered by moving a device (for example, shaking or tilting) or by gesturing towards the device so that sensors or the camera can pick up and interpret these gestures, can also be operated via user interface components, unless the motion is essential for the function and not using it would invalidate the activity.

Note: This criterion concerns input through sensors which respond directly to motions such as tilting, shaking, or gesturing towards a device. It is not intended to cover the motion of users through space as registered by geolocation sensors or beacons, or events observed by the device other than intentional gestures by the user. It also does not cover indirect motion associated with operating a keyboard, pointer, or assistive technology.

Devices often have sensors that can act as inputs, e.g., accelerometer and gyroscope sensors on a phone or tablet device. These sensors can allow the user to control something by simply changing the orientation or moving the device in particular ways. In other situations, web content can interpret user gestures via the camera or other sensors to actuate functions, for example, to move forward or backward in a sequence of pages. Some users with disabilities are not able to operate these device sensors (either not at all or not precisely enough) because the device is affixed to a wheelchair or due to motor impairments. Functionality must therefore be implemented in a way that other means are available to activate the function that do not rely on sensor input.

Some applications are specifically created to use device sensor data. Examples of content that are exempt from this requirement include a pedometer that relies on device motion to count steps.

@@We should clarify that authors may be able to meet this when OS settings for control of a particular type of motion allow the user to disable the motion detection.

Benefits

Examples

Resources

None

Techniques

Sufficient

  • Functionality/content must not solely rely on device inputs (e.g. an alternative which does not require the user to manipulate their device/use these device inputs must be available)

Advisory

Failure

  • Functionality/content solely relies on device inputs (e.g. shaking or tilting)