What is not permitted regarding gear shifting on a railroad track?

The correct answer identifies that shifting of gears is not permitted while on a railroad track. This is because railroad tracks can present sudden, hazardous situations, and a school bus should be fully in control when crossing. Engaging in any gear shifting could lead to a loss of control or unintended responsiveness from the vehicle, especially when navigating a potentially dangerous area such as a railroad crossing.

When approaching or crossing railroad tracks, the bus driver should ensure that the vehicle is in the appropriate gear for steady and safe movement, typically a low gear if applicable. This enhances the vehicle's stability and power as it passes over the tracks, reducing the risk of stalling or getting stuck on the tracks.

The actions of shifting in neutral, shifting from park to drive, or shifting while in motion, may all involve some level of risk or distraction, but they are not as directly related to the critical safety concerns of navigating a railroad track as shifting of gears is. Therefore, the focus is primarily on maintaining control and readiness when approaching such crossings.