Police in The Netherlands are fining drivers of uncovered trailers loaded with maize silage on the road €240 (£210) this autumn. They are worried chopped maize can fall or be blown out of the trailers causing them to skid.

Manufacturer-installed trailer covers can cost thousands, so many have made their own versions. Two systems are typical.

The first consists of two hydraulic valves, a frame and a nylon net. These are positioned along the side of the empty trailer with the frame hydraulically lifted through 270 degrees to cover the trailer once it has been filled.

The other system consists of a rolled up net that is fixed to a metal frame, which can be hydraulically pulled over the full trailer.