A hazard warning light — a bright red rectangle to symbolise sudden braking ahead, or a stationary object in the road — occasionally flashed up on screen.

There are many reversing sensors but all work the same way: sensors set into the bumper send out a signal and 'catch' its reflection from any stationary object.

Motion compensators are usually placed between a floating object and a more stationary object, such as a vessel or a structure fixed to the seabed.

When a moving object impacts the stationary head, coup injuries are typical, while contrecoup injuries are produced when the moving head strikes a stationary object.

In addition, patients note that one stationary object may spontaneously disappear from view as they become aware of another object in the scene.