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Text messages (SMS)

Messages need to be integrated in the interface without distracting or disrupting operators.


Operators use the short message service to send messages, which are not safety-relevant.p>


Accessing and using the message feature must be easy. Composing free text messages with a virtual keyboard requires a lot of attention and may disrupt operators in their work.


The message feature is accessed via a button on the bottom menu bar. The main dialog contains the list of received and sent messages as well as functionality to reply, forward, and compose new messages.

The state chart above shows the flow of interaction. Start to read the chart from top left when the user presses the menu button to open the SMS dialog. Then, templates may be used and managed before proceeding on to actually sending the message. Note that in the “Send SMS to” dialog it is possible to compose recipient lists by invoking the phone book, the call log, and the dial pad.


The sample screenshot shows the main SMS dialog. Note the message display in the status bar and the message above the menu bar indicating a new message just arrived.

Safety Impact

Due to the fact that typing on a virtual keyboad requires a lot of attention and focus, composing free text messages is not ideal from a safety point of view because it might disrupt the operator from other, safety-relevant tasks. Therefore, templates are offered to make composing easier. Notifications are designed for unobtrusiveness

The short message service is technologically based on a store-and-forward principle, therefore, no guarantees can be made when a message is delivered, or if it is delivered at all. Safety assessments conducted by the railway operators have concluded that the short message service must not be used for operational messages, which have to be based on a different technology.

Usability Impact

Error prevention, user satisfaction

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