For coupling to be successfully completed, where must the safety catch of the fifth wheel locking lever be?

The safety catch of the fifth wheel locking lever must be positioned over the locking lever for coupling to be successfully completed. This placement ensures that the locking mechanism is properly engaged and provides an extra layer of security, preventing accidental disconnection during operation. When the safety catch is over the locking lever, it acts as a safeguard, ensuring that if any force tries to disengage the lever, it cannot do so without manually lifting the safety catch first. This design feature is crucial for the safe operation of truck-tractor and trailer combinations, as it helps to maintain a secure connection while on the road.

Each of the other options does not fulfill the necessary safety requirements. For instance, if the safety catch is under or behind the locking lever, it might not adequately engage the lever, leading to potential failure of the coupling during operation. Similarly, having it in front of the locking lever compromises its ability to serve its protective function, allowing for the risk of an unintended uncoupling event. Thus, the requirement for the safety catch to be over the locking lever is essential for ensuring the safety and efficiency of coupling operations.