The correct answer is D. All of above.
A block section is a section of railway track that is used by one train at a time. The block section is protected by a signal that indicates whether the section is clear or occupied. If the signal is green, the train can proceed into the block section. If the signal is red, the train must stop.
In the scenario described in the question, two trains entered the same block section simultaneously. This is a violation of block rules, as only one train is allowed in a block section at a time. The trains were able to stop before colliding, but this was a close call and could have resulted in a serious accident.
The trains passed a danger signal, which is another violation of block rules. A danger signal is a red signal that indicates that the track ahead is occupied or unsafe. Trains must stop when they see a danger signal.
The trains were able to avoid a collision, but this was a close call and could have resulted in a serious accident. This is why it is important to follow block rules and to obey danger signals.
Here is a brief explanation of each option:
- A. Violation of block rules: This is a violation of block rules, as only one train is allowed in a block section at a time.
- B. Passing danger signal: The trains passed a danger signal, which is another violation of block rules.
- C. Save collision: The trains were able to avoid a collision, but this was a close call and could have resulted in a serious accident.
- D. All of above: The trains violated block rules, passed a danger signal, and almost collided.