What is the maximum number of powered axles that can be on line for movement of light engines to comply with regulations?

The correct choice is based on regulations concerning the movement of light engines. The standard states that only one powered axle is allowed for every 120 tons of consist. This requirement is in place to ensure safety and stability during the movement of lighter train configurations that may be more prone to instability or operational issues.

This rule helps manage the distribution of power across the train, minimizing the risk of excessive drawbar forces that could compromise the control and braking performance. By limiting the number of powered axles relative to the weight of the train, it helps maintain safe operating conditions while moving light engines.

Other options suggest different ratios, which do not align with the regulatory standards. Those ratios either allow for too many powered axles per weight of the consist or do not provide a suitable safety margin, making them unsuitable for compliance with established guidelines.