What is the order of emergency braking, of a combination vehicle consisting of a tractor and a trailer equipped with a pneumatic braking system?
Show the correct answer
Correct answer
B. The trailer will start braking first.
Explanation
In the photo, there is a blue tractor with a red two-axle trailer connected, with a yellow grille at the back. During emergency braking of a combination with an air brake system, the trailer starts braking first - answer B.
The brakes of a combination are set so that the trailer brakes slightly ahead of the tractor. Thanks to this, the trailer "pulls" backwards and the combination stays straight. If the tractor braked first (answer C), the moving heavy trailer would push against it and could turn it around or fold the combination like a pocket knife (jackknife), especially on a slippery surface or on a curve. Perfectly simultaneous braking (answer A) is difficult to achieve, and even a small delay of the trailer makes it push against the tractor - hence the deliberate lead. The rules require the trailer brake to be applied with one movement together with the tractor brake. Brake firmly, but without locking the wheels, and keep the tractor's wheels straight.
Legal basis: § 48 para. 2 point 1 letter a and § 49 para. 2 of the Regulation on the technical conditions of vehicles and the scope of their necessary equipment