What defines a solid block of cars?

A solid block of cars is defined as one or more cars that are coupled together, charged, or have not been "off air" for more than 24 hours, and have been tested and inspected. This definition is crucial because it ensures that the cars within the block are ready for transportation and have passed necessary safety protocols.

The mention of being charged indicates that the air brakes are functional, which is vital for safe operation. Additionally, having not been "off air" for more than 24 hours means that the air brake systems have been maintained in an operational state without being disconnected, thus ensuring reliability during transit.

Furthermore, the requirement for the cars to be tested and inspected confirms that they meet safety and operational standards before being transported, reducing risks during travel. This comprehensive understanding of what constitutes a solid block of cars is essential for efficient and safe railway operations.