While driving a truck, what should you see in properly-adjusted external mirrors ("rear-view mirrors")?

In the photo, you can see a set of mirrors - a large main one and a smaller wide-angle one - on an arm next to the pillar of a lorry cab. In correctly adjusted exterior mirrors you should see the area behind the vehicle and the sides of the vehicle - answer B.

The Regulation on the technical conditions of vehicles requires a vehicle to be fitted with mirrors that give the driver the rearward visibility needed for road safety, and the Road Traffic Act requires the design of the vehicle to give a sufficient field of view. You adjust the mirror so that a small part of the side of the body or the semi-trailer is visible at the edge of the image, and the rest of the field shows the lane behind you and next to you. The side of the vehicle alone (answer A) tells you nothing about traffic behind, and the adjacent lane alone (answer C) leaves you without a reference point and makes it harder to judge distance. Remember that in a lorry, the mirrors are the only source of information about what is happening behind the cab - that is why a lorry usually has six of them: two main mirrors, two wide-angle mirrors, a kerb mirror on the passenger side and a front mirror above the windscreen.

Legal basis: Art. 66 para. 1 point 5 of the Road Traffic Act (Prawo o ruchu drogowym); § 11 para. 1 point 5a and Annex No. 12 to the Regulation on the technical conditions of vehicles and the scope of their necessary equipment