The correct answer is D. 2 and 3 are correct.
Automatic signalling systems are designed to improve safety and efficiency on railways. They do this by automatically controlling the movement of trains, without the need for human intervention. This can help to reduce the risk of accidents, and can also help to improve the flow of traffic.
However, automatic signalling systems can also lead to higher operating costs. This is because they require more complex infrastructure, and they also require regular maintenance. Additionally, automatic signalling systems can be more difficult to troubleshoot in the event of a problem.
Overall, automatic signalling systems can offer a number of benefits, but they also come with some drawbacks. It is important to weigh the costs and benefits carefully before deciding whether or not to implement an automatic signalling system.
Here is a brief explanation of each statement:
- Greater risk: Automatic signalling systems can lead to greater risk if they are not properly maintained or if there is a problem with the system. This is because they are designed to operate without human intervention, so if there is a problem, it can go unnoticed for some time.
- Higher efficiency: Automatic signalling systems can lead to higher efficiency because they can control the movement of trains more precisely than humans can. This can help to reduce delays and improve the flow of traffic.
- Avoidance of block instruments: Automatic signalling systems can avoid the need for block instruments, which are devices that are used to control the movement of trains in a section of track. This can save money and improve efficiency.
- Higher operating cost: Automatic signalling systems can have higher operating costs than traditional signalling systems. This is because they require more complex infrastructure and regular maintenance.
I hope this helps!