To reduce pressure in an overcharged train brake system, which initial action should be taken?

To reduce pressure in an overcharged train brake system, adjusting the regulating valve to the desired pressure is the correct action to take. This process allows the engineer to manually set the appropriate brake pipe pressure, ensuring that the system is balanced and effective for operational safety.

When an overcharged system occurs, it means that the brake pipe pressure is higher than necessary for optimal brake performance. Adjusting the regulating valve enables the operator to precisely control the pressure, reducing it to the recommended level for effective braking while maintaining the safety and stability of the train.

This action is essential in ensuring that the brake system operates within the acceptable pressure range, thus preventing potential issues such as brake failure or excessive wear on brake components. Additionally, maintaining proper pressure levels is crucial for responsive braking control.