Explicit communication is necessary because humans can be easily distracted and forget the robot is working next to them. Before starting a task or new motion the robot should signal a warning through sounds, lights, or gestures, which provides an extra layer of safety. Think of the loud beeping signal made by a large truck when it is shifted into reverse. Avoid the perception of unexpected behaviors, which would catch a person off guard and put them into compromised situations. Several robots have practice modes of operations that give people an opportunity to observe the task and learn what to expect. The same lights, graphics, and sounds should be repeatedly used so that the user becomes familiar with the signals that precede the robot’s movement. The mode of communication must be suitable for the environment; for example, sound is less effective in a noisy factory, and light might not be seen when the user’s gaze is occupied by the task in front of her. Again, the Swedish factory worker would have been safe if the robot actually warned him before engaging into action.